Puma Biotechnology (PBYI) 10-K 9 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 20, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	PBYI
Entity Registrant Name	PUMA BIOTECHNOLOGY, INC.
Entity Central Index Key	1,401,667
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		37,719,724
Entity Public Float			$ 2,481,469,190

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 81,698	$ 194,494
Marketable securities		34,982
Accounts receivable, net	9,670
Inventory	2,029
Prepaid expenses and other, current	12,997	6,998
Total current assets	106,394	236,474
Property and equipment, net	4,470	5,153
Prepaid expenses and other, long-term	1,989	6,846
Intangible assets, net	48,355
Restricted cash	4,317	4,317
Total assets	165,525	252,790
Current liabilities:
Accounts payable	27,692	20,035
Accrued expenses	30,648	17,426
Total current liabilities	58,340	37,461
Deferred rent	5,406	5,505
Long term debt	48,477
Total liabilities	112,223	42,966
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock - $.0001 par value; 100,000,000 shares authorized; 37,594,851 shares issued and outstanding at December 31, 2017 and 36,826,010 issued and outstanding at December 31, 2016	4	4
Additional paid-in capital	1,142,213	1,006,344
Receivable from exercise of stock options	(449)
Accumulated other comprehensive loss		(13)
Accumulated deficit	(1,088,466)	(796,511)
Total stockholders' equity	53,302	209,824
Total liabilities and stockholders' equity	$ 165,525	$ 252,790

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	37,594,851	36,826,010
Common stock, shares outstanding	37,594,851	36,826,010

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Product revenue, net	$ 26,185
License revenue	1,500
Total revenue	27,685
Operating costs and expenses:
Cost of sales	5,572
Selling, general and administrative	106,693	$ 53,798	$ 31,808
Research and development	207,810	222,798	208,472
Total operating expense	320,075	276,596	240,280
Loss from operations	(292,390)	(276,596)	(240,280)
Other (expenses) income:
Interest income	1,256	958	971
Interest expense	(720)
Other (expenses) income	(101)	(373)	25
Total other (expenses) income	435	585	996
Net loss	(291,955)	(276,011)	(239,284)
Net loss applicable to common stock	$ (291,955)	$ (276,011)	$ (239,284)
Net loss per common share—basic and diluted	$ (7.85)	$ (8.29)	$ (7.45)
Weighted-average common shares outstanding—basic and diluted	37,169,678	33,295,114	32,126,094

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (291,955)	$ (276,011)	$ (239,284)
Other comprehensive income (loss)
Unrealized gain (loss) on available-for-sale securities	13	134	(52)
Comprehensive loss	$ (291,942)	$ (275,877)	$ (239,336)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Receivables from the Exercises of Options	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2014	$ 117,048	$ 3	$ 399,191	$ (835)	$ (95)	$ (281,216)
Beginning Balance (in shares) at Dec. 31, 2014		30,548,309
Stock-based compensation	94,934		94,934
Exercises of stock options	$ 28,228		27,393	835
Exercises of stock options (in shares)	757,038	757,038
Issuance of performance shares (in shares)		11,495
Issuance of common stock	$ 205,133		205,133
Issuance of common stock (in shares)		1,150,000
Unrealized gain on available-for-sale securities	(52)				(52)
Net loss	(239,284)					(239,284)
Ending Balance at Dec. 31, 2015	206,007	$ 3	726,651		(147)	(520,500)
Ending Balance (in shares) at Dec. 31, 2015		32,466,842
Stock-based compensation	117,264		117,264
Exercises of stock options	$ 576		576
Exercises of stock options (in shares)	43,751	46,668
Issuance of common stock	$ 161,854	$ 1	161,853
Issuance of common stock (in shares)		4,312,500
Unrealized gain on available-for-sale securities	134				134
Net loss	(276,011)					(276,011)
Ending Balance at Dec. 31, 2016	$ 209,824	$ 4	1,006,344		(13)	(796,511)
Ending Balance (in shares) at Dec. 31, 2016	36,826,010	36,826,010
Stock-based compensation	$ 108,735		108,735
Exercises of stock options (in shares)	557,080	557,080
Shares issued or RSUs vested under employee stock plans	$ 26,685		27,134	(449)
Shares issued or RSUs vested under employee stock plans (in shares)		768,841
Unrealized gain on available-for-sale securities	13				$ 13
Net loss	(291,955)					(291,955)
Ending Balance at Dec. 31, 2017	$ 53,302	$ 4	$ 1,142,213	$ (449)		$ (1,088,466)
Ending Balance (in shares) at Dec. 31, 2017	37,594,851	37,594,851

Consolidated Statements of Sto7

Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement Of Stockholders Equity [Abstract]
Issuance of common stock, per share	$ 40	$ 190

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net loss	$ (291,955)	$ (276,011)	$ (239,284)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,811	1,149	776
Built-out allowance received from landlord		2,997	179
Stock-based compensation	108,735	117,264	94,934
Disposal of leasehold improvements		368
Changes in operating assets and liabilities:
Accounts receivable, net	(9,670)
Inventory	(2,029)
Other receivables			1,760
Prepaid expenses and other	(1,142)	3,413	(958)
Accounts payable	7,657	2,231	2,806
Accrued expenses	13,222	2,787	(14,805)
Accrual of deferred rent	(99)	4,112	124
Net cash used in operating activities	(172,470)	(141,690)	(154,468)
Investing activities:
Intangible assets	(50,000)
Purchase of property and equipment	(431)	(4,287)	(1,002)
Restricted cash		(4)	(3,098)
Expenditures for leasehold improvements		(2,997)	(179)
Purchase of available-for-sale securities	(79,729)	(81,794)	(214,806)
Sale/maturity of available-for-sale securities	114,724	231,267	133,222
Net cash provided by (used in) investing activities	(15,436)	142,185	(85,863)
Financing activities:
Net proceeds from issuance of common stock		161,854	205,133
Net proceeds from shares issued under employee stock plans	26,685	576	28,228
Debt issuance costs	(1,575)
Proceeds from long term debt	50,000
Net cash provided by financing activities	75,110	162,430	233,361
Net (decrease) increase in cash and cash equivalents	(112,796)	162,925	(6,970)
Cash and cash equivalents, beginning of period	194,494	31,569	38,539
Cash and cash equivalents, end of period	81,698	$ 194,494	$ 31,569
Supplemental disclosures of non-cash investing and financing activities:
Property and equipment purchases in accounts payable	27
Receivables related to stock option exercises	449
Supplemental disclosure of cash flow information:
Interest paid	$ 334

Business and Basis of Presentat

Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Business and Basis of Presentation	Note 1—Business and Basis of Presentation: Business: Puma Biotechnology, Inc., or the Company, is a biopharmaceutical company based in Los Angeles, California with a focus on the development and commercialization of innovative products to enhance cancer care. The Company in-licenses the global development and commercialization rights to three drug candidates—PB272 (neratinib (oral)), PB272 (neratinib (intravenous)) and PB357. Neratinib is a potent irreversible tyrosine kinase inhibitor that blocks signal transduction through the epidermal growth factor receptors, HER1, HER2 and HER4. Currently, the Company is primarily focused on the development and commercialization of the oral version of neratinib, and its most advanced drug candidates are directed at the treatment of HER2-positive breast cancer. The Company believes that neratinib has clinical application in the treatment of several other cancers as well, including non-small cell lung cancer and other tumor types that over-express or have a mutation in HER2. In November 2012, the Company established and incorporated Puma Biotechnology Ltd., a wholly owned subsidiary, for the sole purpose of serving as the Company’s legal representative in the United Kingdom and the European Union in connection with the Company’s clinical trial activity in those countries. Basis of Presentation: The Company is focused on developing and commercializing neratinib for the treatment of patients with human epidermal growth factor receptor type 2, or HER2-positive, breast cancer, HER2 mutated non-small cell lung cancer, HER2-negative breast cancer that has a HER2 mutation and other solid tumors that have an activating mutation in HER2. The Company has reported a net loss of approximately $292.0 million and negative cash flows from operations of approximately $172.5 million for the year ended December 31, 2017. Management believes that the Company will continue to incur net losses and negative net cash flows from operating activities through the drug development process and early commercialization. The Company has incurred significant operating losses and negative cash flows from operations since its inception, which raises substantial doubt about its ability to continue as a going concern. On July 17, 2017, the Company received U.S. Food and Drug Administration, or FDA, approval for its first product, NERLYNX® (neratinib), formerly known as PB272 (neratinib (oral)), for the extended adjuvant treatment of adult patients with early stage HER2-overexpressed/amplified breast cancer following adjuvant trastuzumab-based therapy. Following FDA approval in July 2017, NERLYNX became available by prescription in the United States, and the Company has commenced commercialization. The Company is exploring methods by which to commercially launch neratinib in the European Union should approval be granted by the European Medicines Agency, or EMA. In addition, the Company is required to make substantial payments to Pfizer upon the achievement of certain milestones, some of which may occur within one year from the date the financial statements are issued, and has contractual obligations for clinical trial contracts, some of which are expected to require payment within one year from the date the financial statements are issued (see Note 11). Commercialization in the United States, and if approved, in the European Union, may require funding in addition to the cash and cash equivalents and marketable securities totaling approximately $81.7 million available at December 31, 2017. While the consolidated financial statements have been prepared on a going concern basis, the Company continues to remain dependent on its ability to obtain sufficient funding to sustain operations and successfully commercialize neratinib in the United States, and, if approved, launch in the European Union. While the Company has been successful in raising financing in the past, there can be no assurance that it will be able to do so in the future. The Company’s ability to obtain funding may be adversely impacted by uncertain market conditions, unfavorable decisions of regulatory authorities or adverse clinical trial results. The outcome of these matters cannot be predicted at this time. The Company’s continued operations will depend on its ability to successfully commercialize NERLYNX, the Company’s only product, and to obtain additional capital through various potential sources, such as equity and debt financing. Since its inception through December 31, 2017, the Company’s financing has primarily been through public offerings of Company common stock, private equity placements and a debt financing. The Company sold shares of its common stock through an underwritten public offering in October 2016 (see Note 8), through which the Company received net proceeds of approximately $161.9 million. On October 31, 2017, the Company entered into a loan agreement with Silicon Valley Bank and Oxford Finance for a term loan of up to $100.0 million, dependent upon the achievement of certain milestones (see Note 7). The Company may need additional financing before it can achieve profitability, if ever. There can be no assurance that additional capital will be available on favorable terms or at all or that any additional capital that the Company is able to obtain will be sufficient to meet its needs. If it is unable to raise additional capital, the Company could likely be forced to curtail desired development activities, which will delay the development of its product candidates.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Significant Accounting Policies	Note 2—Significant Accounting Policies: The significant accounting policies followed in the preparation of these consolidated financial statements are as follows: Financial Instruments The carrying value of financial instruments, such as cash equivalents, accounts receivable and accounts payable, approximate their fair value because of their short-term nature. The carrying value of long-term debt approximates its fair value as the principal amounts outstanding are subject to variable interest rates that are based on market rates which are regularly reset. Use of Estimates: The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the balance sheet, and reported amounts of expenses for the period presented. Accordingly, actual results could differ from those estimates. Significant estimates include estimates for variable consideration for which reserves were established. These estimates are included in the calculation of net revenues and include trade discounts and allowances, product returns, provider chargebacks and discounts, government rebates, payor rebates, and other incentives, such as voluntary patient assistance, and other allowances that are offered within contracts between the Company and its customers, payors, and other indirect customers relating to the Company’s sale of its products. Principles of Consolidation: The consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation. Investment Securities: The Company classifies all investment securities (short term and long term) as available-for-sale, as the sale of such securities may be required prior to maturity to implement management’s strategies. These securities are carried at fair value, with the unrealized gains and losses, reported as a component of accumulated other comprehensive loss in stockholders’ equity until realized. Realized gains and losses from the sale of available-for-sale securities, if any, are determined on a specific identification basis. A decline in the market value of any available-for-sale security below cost that is determined to be other than temporary results in the revaluation of its carrying amount to fair value. The impairment is charged to earnings and a new cost basis for the security is established. Premiums and discounts are amortized or accreted over the life of the related security as an adjustment to yield using the straight-line method. Interest income is recognized when earned. License Fees and Intangible Assets: The Company expenses amounts paid to acquire licenses associated with products under development when the ultimate recoverability of the amounts paid is uncertain and the technology has no alternative future use when acquired. Acquisitions of technology licenses are charged to expense or capitalized based upon the asset achieving technological feasibility in accordance with management’s assessment regarding the ultimate recoverability of the amounts paid and the potential for alternative future use. The Company has determined that technological feasibility for its product candidates is reached when the requisite regulatory approvals are obtained to make the product available for sale. The Company capitalizes technology licenses upon reaching technological feasibility. The Company maintains definite-lived intangible assets related to the Licensor agreement. These assets are amortized over their remaining useful lives, which are estimated based on the shorter of the remaining patent life or the estimated useful life of the underlying product. Intangible assets are amortized using the economic consumption method if anticipated future revenues can be reasonably estimated. The straight-line method is used when future revenues cannot be reasonably estimated. Amortization costs are recorded as part of cost of sales. The Company assesses its intangible assets for impairment if indicators are present or changes in circumstance suggest that impairment may exist. Events that could result in an impairment, or trigger an interim impairment assessment, include the receipt of additional clinical or nonclinical data regarding one of the Company’s drug candidates or a potentially competitive drug candidate, changes in the clinical development program for a drug candidate, or new information regarding potential sales for the drug. If impairment indicators are present or changes in circumstance suggest that impairment may exist, the Company performs a recoverability test by comparing the sum of the estimated undiscounted cash flows of each intangible asset to its carrying value on the consolidated balance sheet. If the undiscounted cash flows used in the recoverability test are less than the carrying value, the Company would determine the fair value of the intangible asset and recognize an impairment loss if the carrying value of the intangible asset exceeds its fair value. In connection with the FDA approval of NERLYNX in July 2017, the Company triggered a one-time milestone payment pursuant to its 2014 license agreement with Pfizer Inc., or the Licensor. The Company capitalized the milestone payment as an intangible asset and is amortizing the asset to cost of sales on a straight-line basis over the estimated useful life of the licensed patent through 2030. The Company recorded amortization expense related to its intangible asset of $1.6 million for the year ended December 31, 2017. As of December 31, 2017, estimated future amortization expense related to the Company’s intangible asset was approximately $3.9 million for each year starting 2018 through 2029, and $1.0 million for 2030. Royalties: Royalties incurred in connection with the Company’s license agreement with the Licensor, as disclosed in Note 11-Commitments and Contingencies, are expensed to cost of sales as revenue from product sales is recognized. Inventory: The Company values its inventories at the lower of cost and estimated net realizable value. The Company determines the cost of its inventories, which includes amounts related to materials and manufacturing overhead, on a first-in, first-out basis. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period, and it writes down any excess and obsolete inventories to their estimated realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded within the cost of sales. The determination of whether inventory costs will be realizable requires estimates by management. If actual market conditions are less favorable than projected by management, additional write-downs of inventory may be required, which would be recorded as a cost of sales in the consolidated statements of operations and comprehensive loss. The Company capitalizes inventory costs associated with the Company’s products after regulatory approval, if any, when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. Inventory acquired prior to receipt of marketing approval of a product candidate is recorded as research and development expense as incurred. Inventory that can be used in either the production of clinical or commercial product is recorded as research and development expense when selected for use in a clinical trial. Starter kits, provided to patients prior to insurance approval, are expensed by the Company to sales and marketing expense as incurred. As of December 31, 2017, the Company’s inventory balance consisted primarily of raw materials purchased subsequent to FDA approval. Revenue Recognition: The Company adopted Accounting Standards Codification (“ASC”) Topic 606 - Revenue from Contracts with Customers (“Topic 606”) on January 1, 2017. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements, and financial instruments. Under Topic 606, an entity recognizes revenue when its customer obtains control of the promised goods or services, in an amount that reflects the consideration which the entity expects to be entitled in exchange for those goods or services. The Company had no contracts with customers until the FDA approved NERLYNX on July 17, 2017. Subsequent to receiving FDA approval, the Company entered into a limited number of arrangements with specialty pharmacies (“SPs”) and specialty distributors (“SDs”) in the United States, referred to as the Customers, to distribute NERLYNX. These arrangements are the Company’s initial contracts with customers. The Company has determined that these sales channels with customers are similar. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract, and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to arrangements that meet the definition of a contract under Topic 606, including when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. For a complete discussion of accounting for product revenue, see Product Revenue, Net Product Revenue, Net: The Company sells NERLYNX to a limited number of SPs and SDs in the United States. These Customers subsequently resell the Company’s products to patients and certain medical centers or hospitals. In addition to distribution agreements with Customers, the Company enters into arrangements with health care providers and payors that provide for government mandated and/or privately negotiated rebates, chargebacks and discounts with respect to the purchase of the Company’s products. The Company recognizes revenue on product sales when the Customer obtains control of the Company's product, which occurs at a point in time (upon delivery). Product revenue is recorded net of applicable reserves for variable consideration, including discounts and allowances. The Company’s payment terms range between 10 and 60 days. Shipping and handling costs for product shipments occur prior to the customer obtaining control of the goods, and are recorded in cost of sales. If taxes should be collected from Customers relating to product sales and remitted to governmental authorities, they will be excluded from revenue. The Company expenses incremental costs of obtaining a contract when incurred, if the expected amortization period of the asset that the Company would have recognized is one year or less. However, no such costs were incurred during the year ended December 31, 2017. Product revenue from each of our customers who individually accounted for 10% or more of total revenues consisted of the following: December 31, 2017 Customer A 38 % Customer B 23 % Customer C 13 % License Revenue: The Company also recognizes license revenue under certain of the Company’s license agreements that are within the scope of ASC 606. The terms of these agreements may contain multiple performance obligations, which may include licenses and research and development activities. The Company evaluates these agreements under ASC 606 to determine the distinct performance obligations. Prior to recognizing revenue, the Company makes estimates of the transaction price, including variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Variable consideration may include nonrefundable upfront license fees, payments for research and development activities, reimbursement of certain third-party costs, payments based upon the achievement of specified milestones, and royalty payments based on product sales derived from the collaboration. If there are multiple distinct performance obligations, the Company allocates the transaction price to each distinct performance obligation based on its relative standalone selling price. The standalone selling price is generally determined based on the prices charged to customers or using expected cost plus margin. Revenue is recognized by measuring the progress toward complete satisfaction of the performance obligations using an input measure. Reserves for Variable Consideration: Revenue from product sales are recorded at the net sales price (transaction price), which includes estimates of variable consideration for which reserves are established. Components of variable consideration include trade discounts and allowances, product returns, provider chargebacks and discounts, government rebates, payor rebates, and other incentives, such as voluntary patient assistance, and other allowances that are offered within contracts between the Company and its Customers, payors, and other indirect customers relating to the Company’s sale of its products. These reserves, as detailed below, are based on the related sales, and are classified as reductions of accounts receivable or a current liability. These estimates take into consideration a range of possible outcomes which are probability-weighted in accordance with the expected value method in Topic 606 for relevant factors such as current contractual and statutory requirements, specific known market events and trends, industry data, and forecasted customer buying and payment patterns. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the respective underlying contracts. The amount of variable consideration which is included in the transaction price may be constrained, and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized under the contract will not occur in a future period. The Company’s analyses also contemplated application of the constraint in accordance with the guidance, under which it determined a material reversal of revenue would not occur in a future period for the estimates detailed below as of December 31, 2017 and, therefore, the transaction price was not reduced further during the year ended December 31, 2017. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. Trade Discounts and Allowances: The Company generally provides Customers with discounts which include incentive fees that are explicitly stated in the Company’s contracts and are recorded as a reduction of revenue in the period the related product revenue is recognized. The reserve for discounts is established in the same period that the related revenue is recognized, as well as reductions to trade receivables, net on the consolidated balance sheets. In addition, the Company compensates its Customers for sales order management, data, and distribution services. However, the Company has determined such services received to date are not distinct from the Company’s sale of products to the Customer and, therefore, these payments have been recorded as a reduction of revenue within the statement of operations and comprehensive loss through December 31, 2017. Product Returns: Consistent with industry practice, the Company offers the SPs and SDs limited product return rights for damaged and expiring product, provided it is within a specified period around the product expiration date as set forth in the applicable individual distribution agreement. The Company estimates the amount of its product sales that may be returned by its Customers and records this estimate as a reduction of revenue in the period the related product revenue is recognized, as well a reduction to trade receivables, net on the consolidated balance sheets. The Company currently estimates product returns using available industry data and its own sales information, including its visibility into the inventory remaining in the distribution channel. The Company has an insignificant amount of returns to date and believes that returns of its products will continue to be minimal. Provider Chargebacks and Discounts: Chargebacks for fees and discounts to providers represent the estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to Customers who directly purchase the product from the Company. Customers charge the Company for the difference between what they pay for the product and the ultimate selling price to the qualified healthcare providers. The reserve for chargebacks is established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability. Chargeback amounts are generally determined at the time of resale to the qualified healthcare provider by Customers, and the Company generally issues payments for such amounts within a few weeks of the Customer’s notification to the Company of the resale. Reserves for chargebacks consist of payments that the Company expects to issue for units that remain in the distribution channel at each reporting period-end that the Company expects will be sold to qualified healthcare providers, and chargebacks that Customers have claimed, but for which the Company has not yet issued a payment. Government Rebates: The Company is subject to discount obligations under state Medicaid programs and Medicare. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included in accrued expenses and other current liabilities on the consolidated balance sheets. For Medicare, the Company also estimates the number of patients in the prescription drug coverage gap for whom the Company will owe an additional liability under the Medicare Part D program. The Company’s liability for these rebates consists of invoices received for claims from prior quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimated future claims that will be made for product that has been recognized as revenue, but which remains in the distribution channel at the end of each reporting period. Payor Rebates: The Company contracts with certain private payor organizations, primarily insurance companies and pharmacy benefit managers, for the payment of rebates with respect to utilization of its products. The Company estimates these rebates and records such estimates in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability. Other Incentives: Other incentives which the Company offers include voluntary patient assistance programs, such as the co-pay assistance program, which are intended to provide financial assistance to qualified commercially-insured patients with prescription drug co-payments required by payors. The calculation of the accrual for co-pay assistance is based on an estimate of claims and the cost per claim that the Company expects to receive associated with product that has been recognized as revenue, but remains in the distribution channel at the end of each reporting period. The adjustments are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included as a component of accrued expenses and other current liabilities on the consolidated balance sheets. Assets Measured at Fair Value on a Recurring Basis: Accounting Standards Codification, or “ASC”, 820, Fair Value Measurement Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets. Level 3: Valuations derived from valuation techniques in which one or more significant inputs are unobservable. Following are the major categories of assets measured at fair value on a recurring basis as of December 31, 2017 and 2016, using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3) (in thousands): December 31, 2017 Level 1 Level 2 Level 3 Total Cash equivalents $ 81,698 $ — $ — $ 81,698 $ 81,698 $ — $ — $ 81,698 December 31, 2016 Level 1 Level 2 Level 3 Total Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper — 5,998 — 5,998 Marketable securities - corporate bonds — 28,984 — 28,984 $ 188,543 $ 34,982 $ — $ 223,525 The Company’s investments in commercial paper, corporate bonds and U.S. government securities are exposed to price fluctuations. The fair value measurements for commercial paper, corporate bonds and U.S. government securities are based upon the quoted prices of similar items in active markets multiplied by the number of securities owned. The following tables summarize the Company’s short-term investments (in thousands): Maturity Amortized Unrealized Estimated December 31, 2017 (in years) cost Gains Losses fair value Cash equivalents $ 81,698 $ — $ — $ 81,698 $ 81,698 $ — $ — $ 81,698 Maturity Amortized Unrealized Estimated December 31, 2016 (in years) cost Gains Losses fair value Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper Less than 1 5,998 — — 5,998 Marketable securities - corporate bonds Less than 1 28,997 — (13 ) 28,984 $ 223,538 $ — $ (13 ) $ 223,525 Concentration of Risk: Financial instruments, which potentially subject the Company to concentrations of credit risk, principally consist of cash and cash equivalents and accounts receivable. The Company’s cash and cash equivalents in excess of the Federal Deposit Insurance Corporation and the Securities Investor Protection Corporation insured limits at December 31, 2017, were approximately $86.7 million. The Company does not believe it is exposed to any significant credit risk due to the quality nature of the financial instruments in which the money is held. Pursuant to the Company’s internal investment policy, investments must be rated A-1/P-1 or better by Standard and Poor’s Rating Service and Moody’s Investors Service at the time of purchase. The Company sells its products in the United States primarily through SPs and SDs. Therefore, wholesale distributors and large pharmacy chains account for a large portion of its trade receivables and net product revenues. The creditworthiness of its customers is continuously monitored, and the Company has internal policies regarding customer credit limits. The Company estimates an allowance for doubtful accounts primarily based on the credit worthiness of our customers, historical payment patterns, aging of receivable balances and general economic conditions. The Company’s success depends on the ability to successfully commercialize NERLYNX. The Company currently has a single product with limited commercial sales experience, which makes it difficult to evaluate the current business, predict the future prospects and forecast financial performance and growth. The Company has invested a significant portion of its efforts and financial resources in the development and commercialization of the lead product, NERLYNX, which was approved by the FDA for the extended adjuvant treatment of early stage, HER2-positive breast cancer in the United States on July 17, 2017, and expect NERLYNX to constitute the vast majority of product revenue for the foreseeable future. The Company’s success depends on its ability to effectively commercialize. The Company relies exclusively on third parties to formulate and manufacture NERLYNX and its drug candidates. The commercialization of NERLYNX and any other drug candidates, if approved, could be stopped, delayed or made less profitable if those third parties fail to provide sufficient quantities of product or fail to do so at acceptable quality levels or prices. The Company has no experience in drug formulation or manufacturing and does not intend to establish its own manufacturing facilities. The Company lacks the resources and expertise to formulate or manufacture NERLYNX and other drug candidates. While the drug candidates were being developed by Pfizer, both the drug substance and drug product were manufactured by third-party contractors. The Company is using the same third-party contractors to manufacture, supply, store and distribute drug supplies for clinical trials and the commercialization of NERLYNX. If the Company is unable to continue its relationships with one or more of these third-party contractors, it could experience delays in the development or commercialization efforts as it locates and qualifies new manufacturers. The Company intends to rely on one or more third-party contractors to manufacture the commercial supply of drugs. Research and Development Expenses: Research and development expenses, or R&D, are charged to operations as incurred. The major components of research and development costs include clinical manufacturing costs, clinical trial expenses, consulting and other third-party costs, salaries and employee benefits, stock-based compensation expense, supplies and materials, and allocations of various overhead costs. Clinical trial expenses include, but are not limited to, investigator fees, site costs, comparator drug costs, and clinical research organization, or CRO, costs. In the normal course of business, the Company contracts with third parties to perform various clinical trial activities in the ongoing development of potential products. The financial terms of these agreements are subject to negotiation and variations from contract to contract and may result in uneven payment flows. Payments under the contracts depend on factors such as the achievement of certain events, the successful enrollment of patients and the completion of portions of the clinical trial or similar conditions. The Company’s accruals for clinical trials are based on estimates of the services received and efforts expended pursuant to contracts with numerous clinical trial sites, cooperative groups and CROs. The objective of the Company’s accrual policy is to match the recording of expenses in the Consolidated Financial Statements to the actual services received and efforts expended. As actual costs become known, the Company adjusts its accruals in that period. In instances where the Company enters into agreements with third parties for clinical trials and other consulting activities, upfront amounts are recorded to prepaid expenses and other in the accompanying Consolidated Balance Sheets and expensed as services are performed or as the underlying goods are delivered. If the Company does not expect the services to be rendered or goods to be delivered, any remaining capitalized amounts for non-refundable upfront payments are charged to expense immediately. Amounts due under such arrangements may be either fixed fee or fee for service, and may include upfront payments, monthly payments and payments upon the completion of milestones or receipt of deliverables. Costs related to the acquisition of technology rights and patents for which development work is still in process are charged to operations as incurred and considered a component of research and development costs. Stock-Based Compensation: Stock option awards: ASC 718, Compensation-Stock Compensation Warrants: Warrants (refer to Note 8 for further details) granted to employees are normally valued at the fair value of the instrument on the grant date and are recognized in the statement of operations over the requisite service period. When the requisite service period precedes the grant date and a market condition exists in the warrant, the Company values the warrant using the Monte Carlo Simulation Method. When the terms of the warrant become fixed, the Company values the warrant using the Black-Scholes Option Pricing Method. As allowed by ASC 718 for companies with a short period of publicly traded stock history, the Company’s estimate of expected volatility is based on the average volatilities of a sampling of eight to nine companies with similar attributes to the Company, including industry, stage of life cycle, size and financial leverage. The risk-free rate for periods within the contractual life of the warrant is based on the U.S. Treasury yield curve in effect at the time of grant valuation. In determining the value of the warrant until the terms are fixed, the Company factors in the probability of the market condition occurring and several possible scenarios. When the requisite service period precedes the grant date and is deemed to be complete, the Company records the fair value of the warrant at the time of issuance as an equity stock-based compensation transaction. The grant date is determined when all pertinent information, such as exercise price and quantity are known. Restricted stock units: The restricted stock units, or RSUs, are valued on the grant date and the fair value of the RSUs is equal to the market price of the Company’s common stock on the grant date. The RSU expense is recognized over the requisite service period. When the requisite service period begins prior to the grant date (because the service inception date occurs prior to the grant date), the Company is required to begin recognizing compensation cost before there is a measurement date (i.e., the grant date). The service inception date is the beginning of the requisite service period. If the service inception date precedes the grant date, accrual of compensation cost for periods before the grant date shall be based on the fair value of the award at the reporting date. In the period in which the grant date occurs, cumulative compensation cost shall be adjusted to reflect the cumulative effect of measuring compensation cost based on fair value at the grant date rather than the fair value previously used at the service inception date (or any subsequent reporting date). Income Taxes: The Company follows Income Taxes , The standard A On December 22, 2017, H.R. 1/Public Law No. 115-97 known as the Tax Cuts and Jobs Act (the “Tax Act”), was signed into law. The effects of this new federal legislation are recognized upon enactment, which is the date a bill is signed into law. The Act includes numerous changes in existing tax law, including a permanent reduction in the federal corporate income tax rate from 35% (as the top corporate tax rate) to 21%. As a result of the Tax Act, the Company has revalued its net deferred tax assets as of December 31, 2017 to reflect the rate reduction. Pursuant to the SEC Staff Accounting Bulletin ("SAB") No. 118, "Income Tax Accounting Implications of the Tax Cuts and Jobs Act" ("SAB 118"), a company may select between one of three scenarios to determine a reasonable estimate arising from the Tax Act. Those scenarios are (i) a final estimate which effectively closes the measurement window; (ii) a reasonable estimate leaving the measurement window open for future revisions; and (iii) no estimate as the law is still being analyze

Prepaid Expenses and Other

Prepaid Expenses and Other	12 Months Ended
	Dec. 31, 2017
Banking And Thrift [Abstract]
Prepaid Expenses and Other	Note 3—Prepaid Expenses and Other: Prepaid expenses and other consisted of the following at December 31 (in thousands): December 31, 2017 December 31, 2016 Current: CRO services $ 7,188 $ 3,471 Other clinical development 878 1,069 Insurance 1,306 1,159 Other 3,625 1,299 12,997 6,998 Long-term: CRO services 860 5,077 Other clinical development 886 1,243 Insurance 26 40 Other 217 486 1,989 6,846 Totals $ 14,986 $ 13,844

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Property and Equipment	Note 4—Property and Equipment: Property and equipment consisted of the following at December 31 (in thousands): Property and Equipment: December 31, 2017 December 31, 2016 Leasehold improvements $ 3,878 $ 3,878 Computer equipment 2,147 1,822 Telephone equipment 302 256 Furniture and fixtures 2,206 2,146 8,533 8,102 Less: accumulated depreciation and amortization (4,063 ) (2,949 ) Totals $ 4,470 $ 5,153

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible Assets	Note 5—Intangible Assets: Intangible assets consisted of the following at December 31 (in thousands): December 31, 2017 Estimated useful life Acquired and in-licensed rights $ 50,000 13 Years Less: accumulated amortization (1,645 ) Total intangible asset, net $ 48,355 Estimated future intangible amortization expense as of December 31, 2017 is as follows (in thousands): 2018 $ 3,947 2019 3,947 2020 3,947 2021 3,947 2022 3,947 Thereafter 28,620 Total $ 48,355

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2017
Payables And Accruals [Abstract]
Accrued Expenses	Note 6—Accrued Expenses: Accrued expenses consisted of the following at December 31 (in thousands): December 31, 2017 December 31, 2016 Accrued CRO services $ 8,335 $ 6,609 Accrued other clinical development 3,438 7,015 Accrued legal fees 2,046 706 Accrued compensation 2,797 1,986 Accrued bonus 3,376 1,072 Accrued royalties 3,922 — Other 6,734 38 Totals $ 30,648 $ 17,426 Accrued CRO services represent the Company’s estimate of such costs and will be adjusted in the period the actual costs become known. Accrued compensation includes estimated bonus and earned but unused vacation for full-time employees. When actual performance bonuses are paid out to employees, the bonus expense will be adjusted to reflect the actual expense for the year. Additionally, vacation is accrued at the rate the employee earns vacation and reduced as vacation is used by the employee and accrued royalties represent royalties incurred in connection with the Company’s license agreement with the Licensor.

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	Note 7—Debt: Long term debt consisted of the following at December 31, 2017 (in thousands): Twelve Months Ended Maturity Date Long term debt $ 50,000 October 31, 2022 Less: deferred financing costs (1,523 ) Total long term debt, net $ 48,477 On October 31, 2017 (the “Effective Date”), the Company entered into a loan and security agreement (the “credit facility”) with Silicon Valley Bank, as administrative and collateral agent (“SVB”), and the lenders party thereto from time to time, including Oxford Finance LLC and SVB, pursuant to which the lenders agreed to make term loans available to the Company in an aggregate amount of $100 million, consisting of (i) an aggregate amount of $50 million available on the Effective Date and (ii) an aggregate amount of $50 million available to be drawn at the Company’s option between March 31, 2018 and June 30, 2018, provided the Company has achieved a specified minimum revenue milestone and no event of default is occurring. Proceeds from the term loans may be used for working capital and general business purposes. The credit facility is secured by substantially all of the Company’s personal property other than its intellectual property. We also pledged 65% of the issued and outstanding capital stock of its subsidiary, Puma Biotechnology Ltd. The credit facility limits its ability to grant any interest in its intellectual property to certain permitted licenses and permitted encumbrances set forth in the agreement. The term loans under the credit facility bear interest at an annual rate equal to the greater of (i) 7.75% and (ii) the sum of (a) the “prime rate,” as reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue, plus (b) 3.5%. The Company is required to make monthly interest-only payments on each outstanding term loan commencing on the first calendar day of the calendar month following the funding date of such term loan, and continuing on the first calendar day of each calendar month thereafter through December 1, 2019. Commencing on December 1, 2019, and continuing on the first calendar day of each calendar month thereafter, the Company is required to make consecutive equal monthly payments of principal, together with applicable interest, in arrears to each lender, calculated pursuant to the credit facility. All unpaid principal and accrued and unpaid interest with respect to each term loan is due and payable in full on October 31, 2022. Upon repayment of the term loans, the Company is also required to make a final payment to the lenders equal to 7.5% of the original principal amount of term loans funded. At the Company’s option, it may prepay the outstanding principal balance of any term loan in whole but not in part, subject to a prepayment fee of 2.0% of any amount prepaid if the prepayment occurs through and including the first anniversary of the funding date of such term loan, or 1.0% of the amount prepaid if the prepayment occurs after the first anniversary of the funding date of such term loan through and including the second anniversary of the funding date of such term loan. The credit facility includes affirmative and negative covenants applicable to the Company, its current subsidiary and any subsidiaries it may create in the future. The affirmative covenants include, among others, covenants requiring the Company to maintain its corporate existence and governmental approvals, deliver certain financial reports, maintain insurance coverage and satisfy certain requirements regarding deposit accounts. The Company must also achieve product revenue, measured as of the last day of each fiscal quarter on a trailing three-month basis, that is (i) greater than or equal to 70% of its revenue target set forth in its board-approved projections for the 2017 fiscal year, (ii) greater than or equal to 50% of its revenue target set forth in its board-approved projections for the 2018 fiscal year, and (iii) greater than or equal to 50% of its revenue target set forth in its board-approved projections for the 2019 fiscal year. New minimum revenue levels will be established for each subsequent fiscal year by mutual agreement of the Company, SVB, as administrative agent, and the lenders. The negative covenants include, among others, restrictions on the Company’s transferring collateral, incurring additional indebtedness, engaging in mergers or acquisitions, paying dividends or making other distributions, making investments, creating liens, selling assets and suffering a change in control, in each case subject to certain exceptions. The credit facility also includes events of default, the occurrence and continuation of which could cause interest to be charged at the rate that is otherwise applicable plus 5.0% and would provide SVB, as collateral agent, with the right to exercise remedies against us and the collateral securing the credit facility, including foreclosure against the property securing the credit facilities, including its cash. These events of default include, among other things, any failure by the Company to pay principal or interest due under the credit facility, a breach of certain covenants under the credit facility, the Company’s insolvency, a material adverse change, the occurrence of any default under certain other indebtedness in an amount greater than $500,000 and one or more judgments against the Company in an amount greater than $500,000 individually or in the aggregate.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	Note 8—Stockholders’ Equity: Common Stock: October 2016 Common Stock Offering. On October 19, 2016, the Company entered into an underwriting agreement in connection with the public offering, issuance and sale by the Company of 3,750,000 shares of the Company’s common stock, par value $0.0001 per share, at a public offering price of $40.00 per share, less underwriting discounts and commissions. Under the terms of the underwriting agreement, the Company also granted the underwriters an option exercisable for 30 days to purchase up to an additional 562,500 shares of its common stock at the public offering prices, less underwriting discounts and commissions. On October 20, 2016, the underwriters exercised their option to purchase additional shares in full. The Company received net proceeds from the offering of approximately $161.9 million, after deducting underwriting discounts and commissions and estimated offering expenses. The Company issued 557,080, 46,668, and 757,038 shares of common stock upon exercise of stock options during the years ended December 31, 2017, 2016 and 2015, respectively. The Company issued 211,761 shares of common stock upon vesting of restricted stock units during the year ended December 31, 2017. Authorized Shares: The Company had 110,000,000 shares of stock authorized for issuance, of which 100,000,000 were common stock, par value $0.0001 per share, and 10,000,000 were preferred stock, par value $0.0001 per share. On October 4, 2011, the Board of Directors of the Company and the stockholders owning 100% of the Company’s issued and outstanding common stock approved an Amended and Restated Certificate of Incorporation, or the Amended Certificate, which eliminated the Company’s entire authorized class of preferred stock and reduced the total number of shares of capital stock that the Company may issue from 110,000,000 shares to 100,000,000 shares, all of which are designated as common stock, par value $0.0001 per share. The Amended Certificate became effective on November 14, 2011, upon the filing of the Amended Certificate with the Secretary of State of the State of Delaware. Warrants: Following the October 2011 common stock offering, Alan Auerbach, the Company’s founder and chief executive officer, held approximately 21% of the 18,666,733 outstanding shares of the Company’s common stock. Pursuant to the terms of the securities purchase agreement, the Company issued an anti-dilutive warrant to Mr. Auerbach. The warrant was issued to provide Mr. Auerbach with the right to maintain ownership of at least 20% of the Company’s common stock in the event that the Company raised capital through the sale of its securities in the future. In connection with the closing of a public offering on October 24, 2012, the exercise price and number of shares underlying the warrant issued to Mr. Auerbach were established and, accordingly, the final value of the warrant became fixed. Pursuant to the terms of the warrant, Mr. Auerbach may exercise the warrant to acquire 2,116,250 shares of the Company’s common stock at $16 per share until October 4, 2021. Stock Options and Restricted Stock Units: The Company’s 2011 Incentive Award Plan, or the 2011 Plan, was adopted by the Board of Directors on September 15, 2011. Pursuant to the 2011 Plan, the Company may grant incentive stock options and nonqualified stock options, as well as other forms of equity-based compensation. Incentive stock options may be granted only to employees, while consultants, employees, officers and directors are eligible for the grant of nonqualified options under the 2011 Plan. The maximum term of stock options granted under the 2011 Plan is 10 years. The exercise price of incentive stock options granted under the 2011 Plan must be at least equal to the fair value of such shares on the date of grant. Through December 31, 2017, a total of 12,529,412 shares of the Company’s common stock have been reserved for issuance under the 2011 Plan. The Company awarded only “plain vanilla options” as determined by the SEC Staff Accounting Bulletin 107, or Share Based Payment The Company’s 2017 Employment Inducement Incentive Award Plan, or the 2017 Plan, was adopted by the board of directors on April 27, 2017. Pursuant to the 2017 Plan, the Company may grant stock options and restricted stock units, as well as other forms of equity-based compensation to employees, as an inducement to join the Company. The maximum term of stock options granted under the 2017 Plan is 10 years. The exercise price of stock options granted under the 2017 Plan must be at least equal to the fair market value of such shares on the date of grant. As of December 31, 2017, a total of 1,000,000 shares of the Company’s common stock have been reserved for issuance under the 2017 Plan. As of December 31, 2017, 233,250 shares have been awarded under the 2017 Plan. 2017 2016 Dividend yield 0.0 % 0.0 % Expected volatility 70.2 % 68.1 % Risk-free interest rate 2.0 % 1.7 % Expected life in years 5.83 5.80 Employee stock-based compensation was as follows for the years ended December 31 (in thousands except per share data): Twelve Months Ended December 31, 2017 2016 2015 Stock-based compensation: Options - Research and development, or R&D $ 67,299 $ 88,049 $ 76,995 Selling, general and administrative, or SG&A 23,024 25,043 17,166 Performance shares - R&D — (528 ) 773 Restricted stock units - Selling, general and administrative, or SG&A 8,170 1,580 — Research and development, or R&D 10,242 3,120 — Total stock-based compensation expense $ 108,735 $ 117,264 $ 94,934 Activity with respect to options granted under the 2011 and 2017 Plan is summarized as follows: Shares Weighted Average Exercise Price Weighted Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2014 3,978,126 $ 89.55 8.7 $ 431,635 Granted 2,606,183 $ 117.62 9.4 — Forfeited (277,140 ) $ 177.98 — — Exercised (757,038 ) $ 36.19 — $ 102,149 Expired (7,846 ) $ 105.42 Outstanding at December 31, 2015 5,542,285 $ 105.59 8.6 $ 87,632 Granted 1,658,465 $ 42.34 9.3 Forfeited (446,544 ) $ 122.50 Exercised (43,751 ) $ 13.16 $ 1,360 Expired (131,933 ) $ 185.10 Outstanding at December 31, 2016 6,578,522 $ 87.52 8.0 $ 18,442 Granted 519,791 $ 38.87 8.4 Forfeited (285,377 ) $ 50.11 Exercised (557,080 ) $ 48.71 $ 27,185 Expired (121,343 ) $ 125.40 Outstanding at December 31, 2017 6,134,513 $ 87.91 7.2 $ 220,060 Nonvested at December 31, 2017 1,788,436 $ 55.52 8.6 $ 82,445 Exercisable at December 31, 2017 4,346,077 $ 101.24 6.6 $ 137,615 At December 31, 2017, total estimated unrecognized employee compensation cost related to non-vested stock options granted prior to that date was approximately $51.3 million, which is expected to be recognized over a weighted-average period of 1.3 years. At December 31, 2017, the total estimated unrecognized employee compensation cost related to non-vested restricted stock units was approximately $116.0 million, which is expected to be recognized over a weighted-average period of 2.6 years. The weighted-average grant date fair value of options granted during the years ended December 31, 2017, 2016 and 2015, was $24.30, $25.69 and $68.30 per share, respectively. The weighted average grant date fair value of restricted stock units awarded during the year ended December 31, 2017 was $94.93. Weighted Average Grant-Date Stock options Shares Fair Value Nonvested shares at December 31, 2015 3,572,202 $ 73.59 Granted 1,658,465 25.69 Vested/Issued (1,678,040 ) 77.69 Forfeited (446,544 ) 73.22 Nonvested shares at December 31, 2016 3,106,083 47.78 Granted 519,791 24.30 Vested/Issued (1,552,061 ) 59.76 Forfeited (285,377 ) 30.21 Nonvested shares at December 31, 2017 1,788,436 $ 33.37 Weighted Average Grant-Date Restricted stock units Shares Fair Value Nonvested shares at December 31, 2015 - $ - Granted 640,644 54.35 Vested/Issued (2,917 ) 54.35 Forfeited (7,219 ) 54.35 Nonvested shares at December 31, 2016 630,508 54.35 Granted 1,277,081 94.93 Vested/Issued (211,761 ) 55.17 Forfeited (58,166 ) 63.02 Nonvested shares at December 31, 2017 1,637,662 $ 85.58

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
	Dec. 31, 2017
Postemployment Benefits [Abstract]
401(k) Savings Plan	Note 9—401(k) Savings Plan: During 2012, the Company adopted a 401(k) savings plan for the benefit of its employees. The Company is required to make matching contributions to the 401(k) plan equal to 100% of the first 3% of wages deferred by each participating employee and 50% on the next 2% of wages deferred by each participating employee. The Company incurred expenses for employer matching contributions of approximately $0.9 million, $1.0 million and $0.7 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Note 10—Income Taxes: We did not have any provision for income taxes for the years ended December 31, 2017, 2016 and 2015. Temporary 2017 2016 Deferred tax assets—2017: Net operating loss carry forwards $ 257,121 $ 209,308 Business credit carryforwards 29,695 21,256 Organization costs 180 177 Compensation 76,423 84,341 Deferred rent - leasehold improvement 680 1,194 Other 806 997 364,905 317,273 Deferred tax liabilities (758 ) (1,269 ) Total deferred tax assets 364,147 316,004 Valuation allowance (364,147 ) (316,004 ) Net deferred tax assets $ — $ — As $48.1 million and respectively and $870.0 million The provision 2017 2016 2015 Tax computed at the federal statutory rate $ (99,234 ) $ (93,839 ) $ (81,356 ) State taxes (15,890 ) (15,693 ) (16,620 ) Permanent items (1,404 ) 6,152 4,225 R&D credits (6,217 ) (2,728 ) (5,029 ) Deferred tax asset adjustment 6,805 — — Other (20 ) (113 ) (2,571 ) Impact of federal statutory rate change related to the 2017 Tax Act 141,147 — — Change in valuation allowance (25,187 ) 106,221 101,351 Total provision $ — $ — $ — The following is a tabular reconciliation of the total amounts of unrecognized tax benefits at December 31:. (in thousands) 2017 2016 2015 Unrecognized tax benefits—January 1 $ 5,315 $ 4,475 $ 2,482 Gross decreases—tax positions in prior period — — — Gross increases—tax positions in current period 1,836 840 1,993 Unrecognized tax benefits—December 31 $ 7,151 $ 5,315 $ 4,475 The unrecognized tax benefits that, if recognized, would affect the effective tax rate is $7.2 million at December 31, 2017. The Company does not have tax positions for which it is reasonably possible that the total amounts of unrecognized tax benefit will significantly increase or decrease within 12 months of the reporting date. The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by the federal and state jurisdictions where applicable. There are currently no pending income tax examinations. The Company’s tax years for 2007 and forward are subject to examination by the federal and California tax authorities due to the carryforward of unutilized net operating losses and research and development credits.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 11—Commitments and Contingencies: Office Leases: On December 7, 2011, the Company, entered into a non-cancelable operating lease for office space in Los Angeles, California. The initial term of the lease is for seven years and commenced on December 10, 2011. The base rent was approximately $44,400 per month during the first year and will increase each year during the initial term, up to approximately $53,000 per month during the seventh year. The lease has an expiration date of December 9, 2018. In addition, the Company has an option to extend the lease for an additional five-year term. The lease is subject to additional charges for common area maintenance and other costs. Concurrent with the execution of the lease, the Company provided the landlord an automatically renewable stand-by letter of credit in the amount of $2,500,000. The stand-by letter of credit is collateralized by a high-yield savings account which is classified as restricted cash on the accompanying Consolidated Balance Sheets. Rent expense for the years ended December 31, 2017, 2016, and 2015, was approximately $3,879,929, $3,547,300 and $1,597,200, respectively. On June 7, 2012, the Company entered into a long-term lease agreement for office space in South San Francisco, California. The initial term of the lease is seven years and commenced on November 1, 2012. The base rent was approximately $20,250 per month during the first year and will increase over the course of the initial term, up to approximately $30,820 per month during the seventh year. In addition, the Company has an option to extend the lease for an additional five-year term, which would commence upon the expiration of the initial term. In the event the Company elects to extend the lease, the minimum monthly rent payable for the additional term will be the then-current fair market rent calculated in accordance with the terms of the lease. The Company provided the landlord an automatically renewable stand-by letter of credit in the amount of $1,591,400. The stand-by letter of credit is collateralized by a high-yield savings account which is classified as restricted cash on the accompanying Consolidated Balance Sheets. On November 28, 2012, the Company entered into an amendment to the lease for its office space in Los Angeles, California. This amendment added approximately 3,500 rentable square feet to the existing lease of approximately 13,250 square feet. Pursuant to the amendment, the Company’s monthly rent increased by approximately $12,145 per month following the execution of the amendment and will be increased to approximately $14,080 per month at the end of the lease term. On December 1, 2013, the Company entered into a second amendment to the lease for its office space in Los Angeles, California. This amendment added approximately 5,949 rentable square feet to the existing lease of approximately 16,750 square feet. Pursuant to the amendment, the Company’s monthly rent increased by approximately $10,400 per month following the execution of the amendment and will be increased to approximately $25,100 per month at the end of the lease term. On March 18, 2014, the Company entered into a third amendment to the lease of its office space in Los Angeles, California. This amendment added approximately 2,908 rentable square feet to the existing lease of approximately 22,775 square feet. Pursuant to the amendment, the Company’s monthly rent expense increased by approximately $11,487 per month following the execution of the amendment and will be increased to approximately $12,928 per month at the end of the lease term. On May 19, 2014, the Company entered into a first amendment to the lease of its office space in South San Francisco, California. This amendment added approximately 7,152 rentable square feet to the existing lease of approximately 9,560 square feet. Pursuant to the amendment, the Company’s monthly rent expense increased by approximately $22,886 per month following the execution of the amendment and will be increased to approximately $27,328 per month during the last year of the lease term. In July 2015, the Company amended its lease to expand the rented square feet in its Los Angeles office by approximately 26,000 square feet. The lease commenced April 1, 2016, and increased the monthly rent in the Los Angeles location by approximately $150,000 per month with annual increases of approximately 3% per year for the 10-year lease term. The amendment also extended the term of the lease until March 2026. In addition, in July 2015, the Company amended its office lease with to expand the rented square feet in its South San Francisco location by approximately 13,000 square feet. The lease commenced April 1, 2016, and increased the monthly rent in the South San Francisco location by approximately $51,400 with annual increases of approximately 3% per year for the 10-year lease term. The amendment also extended the term of the lease until March 2026. In addition, in October 2017, the Company amended its office lease to expand the rented square feet in its Los Angeles location by approximately 14,000 square feet. The lease commences May 1, 2018, and increases the monthly rent in the Los Angeles location by approximately $71,000 with annual increases of approximately 3.5% per year for the 9-year lease term. The amendment also extended the term of the lease until March 2026. The Company also plans to sublease a portion of its existing Los Angeles office space in early 2018. Future minimum lease payments for each of the years subsequent to December 31, 2017, are as follows (in thousands): Year Ending December 31, Amount 2018 $ 4,472 2019 4,859 2020 5,141 2021 5,300 Thereafter 24,090 Total $ 43,862 License Agreement: In August 2011, the Company entered into an agreement pursuant to which Pfizer, Inc., or the Licensor, agreed to grant it a worldwide license for the development, manufacture and commercialization of PB272 neratinib (oral), PB272 neratinib (intravenous) and PB357, and certain related compounds. The license is exclusive with respect to certain patent rights owned by or licensed to the Licensor. Under the agreement, the Company is obligated to commence a new clinical trial for a product containing one of these compounds within a specified period of time and to use commercially reasonable efforts to complete clinical trials and to achieve certain milestones as provided in a development plan. From the closing date of the agreement through December 31, 2011, the Licensor continued to conduct the existing clinical trials on behalf of the Company at the Licensor’s sole expense. At the Company’s request, the Licensor has agreed to continue to perform certain services in support of the existing clinical trials at the Company’s expense. These services will continue through the completion of the transitioned clinical trials. The license agreement “capped” the out of pocket expense the Company would be responsible for completing the then existing clinical trials. All agreed upon costs incurred by the Company above the “cost cap” would be reimbursed by the Licensor. The Company exceeded the “cost cap” during the fourth quarter of 2012. In accordance with the license agreement, the Company billed the Licensor for agreed upon costs above the “cost cap” until December 31, 2013. On July 18, 2014, the Company entered into an amendment to the license agreement with the Licensor. The amendment amends the License Agreement to (1) reduce the royalty rate payable by the Company to the Licensor on sales of licensed products; (2) release the Licensor from its obligation to pay for certain out-of-pocket costs incurred or accrued on or after January 1, 2014 to complete certain ongoing clinical studies; and (3) provide that the Licensor and the Company will continue to cooperate to effect the transfer to the Company of certain records, regulatory filings, materials and inventory controlled by Licensor as promptly as reasonably practicable. As consideration for the license, the Company is required to make substantial payments upon the achievement of certain milestones totaling approximately $187.5 million if all such milestones are achieved. In connection with the FDA approval of NERLYNX in July of 2017, the Company triggered a one-time milestone payment pursuant to the agreement. Should the Company commercialize any more of the compounds licensed from the Licensor or any products containing any of these compounds, the Company will be obligated to pay to the Licensor annual royalties at a fixed rate in the low-to-mid teens of net sales of all such products, subject to certain reductions and offsets in some circumstances. The Company’s royalty obligation continues, on a product-by-product and country-by-country basis, until the later of (1) the last to expire licensed patent covering the applicable licensed product in such country, or (2) the earlier of generic competition for such licensed product reaching a certain level in such country or expiration of a certain time period after first commercial sale of such licensed product in such country. In the event that the Company sublicenses the rights granted to the Company under the license agreement with the Licensor to a third party, the same milestone and royalty payments are required. The Company can terminate the license agreement at will at any time after April 4, 2013, or for safety concerns, in each case upon specified advance notice. Clinical Trial Contracts: The Company engages with clinical research organizations and contract manufacturing organizations, or CMOs, in addition to engaging in contracts for the management of its ongoing clinical trials and pre-commercialization efforts. The Company may cancel these agreements with a 30 to 45 day written notice to the outside vendor. The Company would be obligated to pay for services rendered up to that point. The contracts also contain variable costs that are hard to predict as they are based on such things as patients enrolled and clinical trial sites, which can vary and therefore, are not included in the table below. The contracts held by the Company as of December 31, 2017, are summarized as follows (in thousands): Indication Estimated Contractual Obligation as of December 31, 2017 Months Remaining on Contract HER2 Overexpressed/Amplified Breast Cancer (Extension) $ 20,323 24 HER2 Overexpressed/Amplified Breast Cancer (Licensor Legacy Clinical Trials) 1,137 12 HER2 Mutated Non-Small Cell Lung Cancer 185 12 HER2 Mutated Breast Cancer and HER2 Mutated Breast Cancer with Brain Mets 5,478 23 Metastatic & Adjuvant Breast Cancer 34,982 32 Neoadjuvant Breast Cancer 3,636 12 Preclinical Research 20,150 40 HER2 Mutated Solid Tumors 10,359 24 Other 20,736 24 Total $ 116,986 Included in the above are payments to be made when milestones are reached. As of December 31, 2017, Company obligations for potential milestone payments totaled approximately $22.2 million. This amount will be paid by the Company if all milestones are reached and would reduce the overall contractual obligation if one or more milestone is never reached. Legal Proceedings The Company and certain of our executive officers were named as defendants in the lawsuits detailed below. Due to the stage of these proceedings, the Company cannot reasonably predict the outcome, nor can it estimate the amount of loss or range of loss, if any, that may result. The Company records a liability in the consolidated financial statements for loss contingencies when a loss is known or considered probable and the amount can be reasonably estimated. If the reasonable estimate of a known or probable loss is a range, and no amount within the range is a better estimate than any other, the minimum amount of the range is accrued. If a loss is reasonably possible but not known or probable, and can be reasonably estimated, the estimated loss or range of loss is disclosed. When determining the estimated loss or range of loss, significant judgment is required to estimate the amount and timing of a loss to be recorded. Hsu vs. Puma Biotechnology, Inc., et. al. On June 3, 2015, Hsingching Hsu or the “plaintiff,” individually and on behalf of all others similarly situated, filed a class action lawsuit against the Company and certain of the Company’s executive officers in the United States District Court for the Central District of California (Case No. 8:15-cv-00865-AG-JCG). On October 16, 2015, lead plaintiff Norfolk Pension Fund filed a consolidated complaint on behalf of all persons who purchased the Company’s securities between July 22, 2014 and May 29, 2015. The consolidated complaint alleges that the Company and certain of its executive officers made false or misleading statements and failed to disclose material adverse facts about its business, operations, prospects and performance in violation of Sections 10(b) (and Rule 10b-5 promulgated thereunder) and 20(a) of the Exchange Act. The plaintiff seeks damages, interest, costs, attorneys' fees, and other unspecified equitable relief. On September 30, 2016, the court denied the defendants’ motion to dismiss the consolidated complaint. On June 6, 2017, the lead plaintiff filed a first amended complaint that included new claims about additional statements that plaintiff alleges are false or misleading. On June 19, 2017, the defendants moved to dismiss the new claims in the amended complaint. On July 25, 2017, the court denied the motion to dismiss. A trial date is currently set for November 6, 2018. The Company intends to vigorously defend against this matter. Eshelman vs. Puma Biotechnology, Inc., et. al. On February 2, 2016, Fredric N. Eshelman filed a lawsuit against the Company’s Chief Executive Officer and President, Alan H. Auerbach, and the Company in the United States District Court for the Eastern District of North Carolina (Case No. 7:16-cv-00018-D). The complaint generally alleges that Mr. Auerbach and the Company made defamatory statements regarding Dr. Eshelman in connection with a proxy contest. Dr. Eshelman seeks compensatory and punitive damages and expenses and costs, including attorneys’ fees. On April 4, 2016, the Company filed a motion to dismiss the complaint. On May 2, 2016, Dr. Eshelman filed a notice of voluntary dismissal of the claims against Mr. Auerbach. On February 6, 2017, the court denied the Company’s motion to dismiss. Discovery ended in September 2017. The Company intends to vigorously defend against Dr. Eshelman’s claims. Derivative Actions On April 12 and April 14, 2016, alleged shareholders filed two derivative lawsuits purportedly on behalf of the Company against certain of the Company’s officers and directors in the Superior Court of the State of California, Los Angeles, captioned Xing Xie v. Alan H. Auerbach, No. BC616617, and Kevin McKenney v. Auerbach, No. BC617059. The complaints assert claims for breach of fiduciary duty, unjust enrichment, abuse of control, mismanagement and waste of corporate assets arising from substantially similar allegations as those contained in the securities class action described above. The complaints seek an unspecified sum of damages and equitable relief. The Company intends to vigorously defend against this matter. Separately, on February 9, 2018, another alleged shareholder filed a derivative lawsuit purportedly on behalf of the Company against certain of its officers and directors in the United States District Court, Central District of California, captioned Arnaud Van Der Gracht De Rommerswael vs. Alan H. Auerbach, et al., No. 8:18-cv-00236. The complaint asserts claims for violation of securities law, breach of fiduciary duty, waste of corporate assets, and unjust enrichment arising from substantially similar allegations as those contained in the securities class action described above. The complaint seeks an unspecified sum of damages, corporate reforms, equitable relief, and restitution. The Company intends to vigorously defend against this matter. Stockholder Demand On September 13, 2017, a purported stockholder filed a complaint in the Court of Chancery of the State of Delaware seeking an equitable apportionment of attorneys’ fees in an unspecified amount. The purported stockholder alleges that his actions caused Company’s board of directors to implement certain governance reforms and enhancements to its director compensation program, and that, as a result of his actions, the purported stockholder is entitled to attorneys’ fees in an amount commensurate to those purported benefits. The Company filed an answer to the complaint on October 20, 2017. The Company intends to vigorously defend against this matter. The pending proceedings described in this section involve complex questions of fact and law and will require the expenditure of significant funds and the diversion of other resources to defend. The results of legal proceedings are inherently uncertain, and material adverse outcomes are possible.

Quarterly Financial Data

Quarterly Financial Data	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	Note 12—Quarterly Financial Data: Quarterly financial data (in thousands except share and per share data): (unaudited) Three Months Ended March 31, June 30, September 30, December 31, 2017 Revenues $ — $ — $ 6,077 $ 21,608 Net loss 72,865 77,832 77,180 64,078 Net loss attributable to common stock 72,865 77,832 77,180 64,078 Net loss per share—basic and diluted $ 1.97 $ 2.10 $ 2.07 $ 1.71 Weighted-average common shares outstanding—basic and diluted 36,931,167 36,992,017 37,214,002 37,534,410 2016 Revenues $ — $ — $ — $ — Net loss (70,972 ) (66,597 ) (65,781 ) (72,661 ) Net loss attributable to common stock (70,972 ) (66,597 ) (65,781 ) (72,661 ) Net loss per share—basic and diluted $ (2.19 ) $ (2.05 ) $ (2.02 ) $ (2.04 ) Weighted-average common shares outstanding—basic and diluted 32,478,408 32,493,092 32,497,168 35,694,193 2015 Revenues $ — $ — $ — $ — Net loss (52,454 ) (64,694 ) (60,417 ) (61,719 ) Net loss attributable to common stock (52,454 ) (64,694 ) (60,417 ) (61,719 ) Net loss per share—basic and diluted $ (1.66 ) $ (2.01 ) $ (1.87 ) $ (1.90 ) Weighted-average common shares outstanding—basic and diluted 31,588,315 32,158,108 32,303,203 32,444,270

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Note 13—Subsequent Events: On January 30, 2018, the Company entered into an agreement with CANbridge Life Sciences, a biopharmaceutical company focused on developing Western drug candidates in China and North Asia, have entered into an exclusive agreement under which CANbridge will develop and commercialize NERLYNX in mainland China, Taiwan, Hong Kong, and Macau (the “Territory”). CANbridge will be responsible for seeking the requisite regulatory approval and, once approved, for commercializing NERLYNX in the Territory. Pursuant to the terms of the agreement, the Company is entitled to receive an upfront payment of $30 million and potential milestone payments totaling up to $40 million upon achievement of certain regulatory milestones and sales-based milestone payments totaling up to $185 million. In addition, the Company is entitled to receive significant double-digit royalties calculated as a percentage of net sales of NERLYNX in the Territory.

Significant Accounting Polici22

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Financial Instruments	Financial Instruments The carrying value of financial instruments, such as cash equivalents, accounts receivable and accounts payable, approximate their fair value because of their short-term nature. The carrying value of long-term debt approximates its fair value as the principal amounts outstanding are subject to variable interest rates that are based on market rates which are regularly reset.
Use of Estimates	Use of Estimates: The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the balance sheet, and reported amounts of expenses for the period presented. Accordingly, actual results could differ from those estimates. Significant estimates include estimates for variable consideration for which reserves were established. These estimates are included in the calculation of net revenues and include trade discounts and allowances, product returns, provider chargebacks and discounts, government rebates, payor rebates, and other incentives, such as voluntary patient assistance, and other allowances that are offered within contracts between the Company and its customers, payors, and other indirect customers relating to the Company’s sale of its products.
Principles of Consolidation	Principles of Consolidation: The consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation.
Investment Securities	Investment Securities: The Company classifies all investment securities (short term and long term) as available-for-sale, as the sale of such securities may be required prior to maturity to implement management’s strategies. These securities are carried at fair value, with the unrealized gains and losses, reported as a component of accumulated other comprehensive loss in stockholders’ equity until realized. Realized gains and losses from the sale of available-for-sale securities, if any, are determined on a specific identification basis. A decline in the market value of any available-for-sale security below cost that is determined to be other than temporary results in the revaluation of its carrying amount to fair value. The impairment is charged to earnings and a new cost basis for the security is established. Premiums and discounts are amortized or accreted over the life of the related security as an adjustment to yield using the straight-line method. Interest income is recognized when earned.
License Fees and Intangible Assets	License Fees and Intangible Assets: The Company expenses amounts paid to acquire licenses associated with products under development when the ultimate recoverability of the amounts paid is uncertain and the technology has no alternative future use when acquired. Acquisitions of technology licenses are charged to expense or capitalized based upon the asset achieving technological feasibility in accordance with management’s assessment regarding the ultimate recoverability of the amounts paid and the potential for alternative future use. The Company has determined that technological feasibility for its product candidates is reached when the requisite regulatory approvals are obtained to make the product available for sale. The Company capitalizes technology licenses upon reaching technological feasibility. The Company maintains definite-lived intangible assets related to the Licensor agreement. These assets are amortized over their remaining useful lives, which are estimated based on the shorter of the remaining patent life or the estimated useful life of the underlying product. Intangible assets are amortized using the economic consumption method if anticipated future revenues can be reasonably estimated. The straight-line method is used when future revenues cannot be reasonably estimated. Amortization costs are recorded as part of cost of sales. The Company assesses its intangible assets for impairment if indicators are present or changes in circumstance suggest that impairment may exist. Events that could result in an impairment, or trigger an interim impairment assessment, include the receipt of additional clinical or nonclinical data regarding one of the Company’s drug candidates or a potentially competitive drug candidate, changes in the clinical development program for a drug candidate, or new information regarding potential sales for the drug. If impairment indicators are present or changes in circumstance suggest that impairment may exist, the Company performs a recoverability test by comparing the sum of the estimated undiscounted cash flows of each intangible asset to its carrying value on the consolidated balance sheet. If the undiscounted cash flows used in the recoverability test are less than the carrying value, the Company would determine the fair value of the intangible asset and recognize an impairment loss if the carrying value of the intangible asset exceeds its fair value. In connection with the FDA approval of NERLYNX in July 2017, the Company triggered a one-time milestone payment pursuant to its 2014 license agreement with Pfizer Inc., or the Licensor. The Company capitalized the milestone payment as an intangible asset and is amortizing the asset to cost of sales on a straight-line basis over the estimated useful life of the licensed patent through 2030. The Company recorded amortization expense related to its intangible asset of $1.6 million for the year ended December 31, 2017. As of December 31, 2017, estimated future amortization expense related to the Company’s intangible asset was approximately $3.9 million for each year starting 2018 through 2029, and $1.0 million for 2030.
Royalties	Royalties: Royalties incurred in connection with the Company’s license agreement with the Licensor, as disclosed in Note 11-Commitments and Contingencies, are expensed to cost of sales as revenue from product sales is recognized.
Inventory	Inventory: The Company values its inventories at the lower of cost and estimated net realizable value. The Company determines the cost of its inventories, which includes amounts related to materials and manufacturing overhead, on a first-in, first-out basis. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period, and it writes down any excess and obsolete inventories to their estimated realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded within the cost of sales. The determination of whether inventory costs will be realizable requires estimates by management. If actual market conditions are less favorable than projected by management, additional write-downs of inventory may be required, which would be recorded as a cost of sales in the consolidated statements of operations and comprehensive loss. The Company capitalizes inventory costs associated with the Company’s products after regulatory approval, if any, when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. Inventory acquired prior to receipt of marketing approval of a product candidate is recorded as research and development expense as incurred. Inventory that can be used in either the production of clinical or commercial product is recorded as research and development expense when selected for use in a clinical trial. Starter kits, provided to patients prior to insurance approval, are expensed by the Company to sales and marketing expense as incurred. As of December 31, 2017, the Company’s inventory balance consisted primarily of raw materials purchased subsequent to FDA approval.
Revenue Recognition	Revenue Recognition: The Company adopted Accounting Standards Codification (“ASC”) Topic 606 - Revenue from Contracts with Customers (“Topic 606”) on January 1, 2017. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements, and financial instruments. Under Topic 606, an entity recognizes revenue when its customer obtains control of the promised goods or services, in an amount that reflects the consideration which the entity expects to be entitled in exchange for those goods or services. The Company had no contracts with customers until the FDA approved NERLYNX on July 17, 2017. Subsequent to receiving FDA approval, the Company entered into a limited number of arrangements with specialty pharmacies (“SPs”) and specialty distributors (“SDs”) in the United States, referred to as the Customers, to distribute NERLYNX. These arrangements are the Company’s initial contracts with customers. The Company has determined that these sales channels with customers are similar. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract, and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to arrangements that meet the definition of a contract under Topic 606, including when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. For a complete discussion of accounting for product revenue, see Product Revenue, Net Product Revenue, Net: The Company sells NERLYNX to a limited number of SPs and SDs in the United States. These Customers subsequently resell the Company’s products to patients and certain medical centers or hospitals. In addition to distribution agreements with Customers, the Company enters into arrangements with health care providers and payors that provide for government mandated and/or privately negotiated rebates, chargebacks and discounts with respect to the purchase of the Company’s products. The Company recognizes revenue on product sales when the Customer obtains control of the Company's product, which occurs at a point in time (upon delivery). Product revenue is recorded net of applicable reserves for variable consideration, including discounts and allowances. The Company’s payment terms range between 10 and 60 days. Shipping and handling costs for product shipments occur prior to the customer obtaining control of the goods, and are recorded in cost of sales. If taxes should be collected from Customers relating to product sales and remitted to governmental authorities, they will be excluded from revenue. The Company expenses incremental costs of obtaining a contract when incurred, if the expected amortization period of the asset that the Company would have recognized is one year or less. However, no such costs were incurred during the year ended December 31, 2017. Product revenue from each of our customers who individually accounted for 10% or more of total revenues consisted of the following: December 31, 2017 Customer A 38 % Customer B 23 % Customer C 13 % License Revenue: The Company also recognizes license revenue under certain of the Company’s license agreements that are within the scope of ASC 606. The terms of these agreements may contain multiple performance obligations, which may include licenses and research and development activities. The Company evaluates these agreements under ASC 606 to determine the distinct performance obligations. Prior to recognizing revenue, the Company makes estimates of the transaction price, including variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Variable consideration may include nonrefundable upfront license fees, payments for research and development activities, reimbursement of certain third-party costs, payments based upon the achievement of specified milestones, and royalty payments based on product sales derived from the collaboration. If there are multiple distinct performance obligations, the Company allocates the transaction price to each distinct performance obligation based on its relative standalone selling price. The standalone selling price is generally determined based on the prices charged to customers or using expected cost plus margin. Revenue is recognized by measuring the progress toward complete satisfaction of the performance obligations using an input measure. Reserves for Variable Consideration: Revenue from product sales are recorded at the net sales price (transaction price), which includes estimates of variable consideration for which reserves are established. Components of variable consideration include trade discounts and allowances, product returns, provider chargebacks and discounts, government rebates, payor rebates, and other incentives, such as voluntary patient assistance, and other allowances that are offered within contracts between the Company and its Customers, payors, and other indirect customers relating to the Company’s sale of its products. These reserves, as detailed below, are based on the related sales, and are classified as reductions of accounts receivable or a current liability. These estimates take into consideration a range of possible outcomes which are probability-weighted in accordance with the expected value method in Topic 606 for relevant factors such as current contractual and statutory requirements, specific known market events and trends, industry data, and forecasted customer buying and payment patterns. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the respective underlying contracts. The amount of variable consideration which is included in the transaction price may be constrained, and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized under the contract will not occur in a future period. The Company’s analyses also contemplated application of the constraint in accordance with the guidance, under which it determined a material reversal of revenue would not occur in a future period for the estimates detailed below as of December 31, 2017 and, therefore, the transaction price was not reduced further during the year ended December 31, 2017. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. Trade Discounts and Allowances: The Company generally provides Customers with discounts which include incentive fees that are explicitly stated in the Company’s contracts and are recorded as a reduction of revenue in the period the related product revenue is recognized. The reserve for discounts is established in the same period that the related revenue is recognized, as well as reductions to trade receivables, net on the consolidated balance sheets. In addition, the Company compensates its Customers for sales order management, data, and distribution services. However, the Company has determined such services received to date are not distinct from the Company’s sale of products to the Customer and, therefore, these payments have been recorded as a reduction of revenue within the statement of operations and comprehensive loss through December 31, 2017. Product Returns: Consistent with industry practice, the Company offers the SPs and SDs limited product return rights for damaged and expiring product, provided it is within a specified period around the product expiration date as set forth in the applicable individual distribution agreement. The Company estimates the amount of its product sales that may be returned by its Customers and records this estimate as a reduction of revenue in the period the related product revenue is recognized, as well a reduction to trade receivables, net on the consolidated balance sheets. The Company currently estimates product returns using available industry data and its own sales information, including its visibility into the inventory remaining in the distribution channel. The Company has an insignificant amount of returns to date and believes that returns of its products will continue to be minimal. Provider Chargebacks and Discounts: Chargebacks for fees and discounts to providers represent the estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to Customers who directly purchase the product from the Company. Customers charge the Company for the difference between what they pay for the product and the ultimate selling price to the qualified healthcare providers. The reserve for chargebacks is established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability. Chargeback amounts are generally determined at the time of resale to the qualified healthcare provider by Customers, and the Company generally issues payments for such amounts within a few weeks of the Customer’s notification to the Company of the resale. Reserves for chargebacks consist of payments that the Company expects to issue for units that remain in the distribution channel at each reporting period-end that the Company expects will be sold to qualified healthcare providers, and chargebacks that Customers have claimed, but for which the Company has not yet issued a payment. Government Rebates: The Company is subject to discount obligations under state Medicaid programs and Medicare. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included in accrued expenses and other current liabilities on the consolidated balance sheets. For Medicare, the Company also estimates the number of patients in the prescription drug coverage gap for whom the Company will owe an additional liability under the Medicare Part D program. The Company’s liability for these rebates consists of invoices received for claims from prior quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimated future claims that will be made for product that has been recognized as revenue, but which remains in the distribution channel at the end of each reporting period. Payor Rebates: The Company contracts with certain private payor organizations, primarily insurance companies and pharmacy benefit managers, for the payment of rebates with respect to utilization of its products. The Company estimates these rebates and records such estimates in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability. Other Incentives: Other incentives which the Company offers include voluntary patient assistance programs, such as the co-pay assistance program, which are intended to provide financial assistance to qualified commercially-insured patients with prescription drug co-payments required by payors. The calculation of the accrual for co-pay assistance is based on an estimate of claims and the cost per claim that the Company expects to receive associated with product that has been recognized as revenue, but remains in the distribution channel at the end of each reporting period. The adjustments are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included as a component of accrued expenses and other current liabilities on the consolidated balance sheets.
Assets Measured at Fair Value on a Recurring Basis	Assets Measured at Fair Value on a Recurring Basis: Accounting Standards Codification, or “ASC”, 820, Fair Value Measurement Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets. Level 3: Valuations derived from valuation techniques in which one or more significant inputs are unobservable. Following are the major categories of assets measured at fair value on a recurring basis as of December 31, 2017 and 2016, using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3) (in thousands): December 31, 2017 Level 1 Level 2 Level 3 Total Cash equivalents $ 81,698 $ — $ — $ 81,698 $ 81,698 $ — $ — $ 81,698 December 31, 2016 Level 1 Level 2 Level 3 Total Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper — 5,998 — 5,998 Marketable securities - corporate bonds — 28,984 — 28,984 $ 188,543 $ 34,982 $ — $ 223,525 The Company’s investments in commercial paper, corporate bonds and U.S. government securities are exposed to price fluctuations. The fair value measurements for commercial paper, corporate bonds and U.S. government securities are based upon the quoted prices of similar items in active markets multiplied by the number of securities owned. The following tables summarize the Company’s short-term investments (in thousands): Maturity Amortized Unrealized Estimated December 31, 2017 (in years) cost Gains Losses fair value Cash equivalents $ 81,698 $ — $ — $ 81,698 $ 81,698 $ — $ — $ 81,698 Maturity Amortized Unrealized Estimated December 31, 2016 (in years) cost Gains Losses fair value Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper Less than 1 5,998 — — 5,998 Marketable securities - corporate bonds Less than 1 28,997 — (13 ) 28,984 $ 223,538 $ — $ (13 ) $ 223,525
Concentration of Risk	Concentration of Risk: Financial instruments, which potentially subject the Company to concentrations of credit risk, principally consist of cash and cash equivalents and accounts receivable. The Company’s cash and cash equivalents in excess of the Federal Deposit Insurance Corporation and the Securities Investor Protection Corporation insured limits at December 31, 2017, were approximately $86.7 million. The Company does not believe it is exposed to any significant credit risk due to the quality nature of the financial instruments in which the money is held. Pursuant to the Company’s internal investment policy, investments must be rated A-1/P-1 or better by Standard and Poor’s Rating Service and Moody’s Investors Service at the time of purchase. The Company sells its products in the United States primarily through SPs and SDs. Therefore, wholesale distributors and large pharmacy chains account for a large portion of its trade receivables and net product revenues. The creditworthiness of its customers is continuously monitored, and the Company has internal policies regarding customer credit limits. The Company estimates an allowance for doubtful accounts primarily based on the credit worthiness of our customers, historical payment patterns, aging of receivable balances and general economic conditions. The Company’s success depends on the ability to successfully commercialize NERLYNX. The Company currently has a single product with limited commercial sales experience, which makes it difficult to evaluate the current business, predict the future prospects and forecast financial performance and growth. The Company has invested a significant portion of its efforts and financial resources in the development and commercialization of the lead product, NERLYNX, which was approved by the FDA for the extended adjuvant treatment of early stage, HER2-positive breast cancer in the United States on July 17, 2017, and expect NERLYNX to constitute the vast majority of product revenue for the foreseeable future. The Company’s success depends on its ability to effectively commercialize. The Company relies exclusively on third parties to formulate and manufacture NERLYNX and its drug candidates. The commercialization of NERLYNX and any other drug candidates, if approved, could be stopped, delayed or made less profitable if those third parties fail to provide sufficient quantities of product or fail to do so at acceptable quality levels or prices. The Company has no experience in drug formulation or manufacturing and does not intend to establish its own manufacturing facilities. The Company lacks the resources and expertise to formulate or manufacture NERLYNX and other drug candidates. While the drug candidates were being developed by Pfizer, both the drug substance and drug product were manufactured by third-party contractors. The Company is using the same third-party contractors to manufacture, supply, store and distribute drug supplies for clinical trials and the commercialization of NERLYNX. If the Company is unable to continue its relationships with one or more of these third-party contractors, it could experience delays in the development or commercialization efforts as it locates and qualifies new manufacturers. The Company intends to rely on one or more third-party contractors to manufacture the commercial supply of drugs.
Research and Development Expenses	Research and Development Expenses: Research and development expenses, or R&D, are charged to operations as incurred. The major components of research and development costs include clinical manufacturing costs, clinical trial expenses, consulting and other third-party costs, salaries and employee benefits, stock-based compensation expense, supplies and materials, and allocations of various overhead costs. Clinical trial expenses include, but are not limited to, investigator fees, site costs, comparator drug costs, and clinical research organization, or CRO, costs. In the normal course of business, the Company contracts with third parties to perform various clinical trial activities in the ongoing development of potential products. The financial terms of these agreements are subject to negotiation and variations from contract to contract and may result in uneven payment flows. Payments under the contracts depend on factors such as the achievement of certain events, the successful enrollment of patients and the completion of portions of the clinical trial or similar conditions. The Company’s accruals for clinical trials are based on estimates of the services received and efforts expended pursuant to contracts with numerous clinical trial sites, cooperative groups and CROs. The objective of the Company’s accrual policy is to match the recording of expenses in the Consolidated Financial Statements to the actual services received and efforts expended. As actual costs become known, the Company adjusts its accruals in that period. In instances where the Company enters into agreements with third parties for clinical trials and other consulting activities, upfront amounts are recorded to prepaid expenses and other in the accompanying Consolidated Balance Sheets and expensed as services are performed or as the underlying goods are delivered. If the Company does not expect the services to be rendered or goods to be delivered, any remaining capitalized amounts for non-refundable upfront payments are charged to expense immediately. Amounts due under such arrangements may be either fixed fee or fee for service, and may include upfront payments, monthly payments and payments upon the completion of milestones or receipt of deliverables. Costs related to the acquisition of technology rights and patents for which development work is still in process are charged to operations as incurred and considered a component of research and development costs.
Stock-Based Compensation	Stock-Based Compensation: Stock option awards: ASC 718, Compensation-Stock Compensation Warrants: Warrants (refer to Note 8 for further details) granted to employees are normally valued at the fair value of the instrument on the grant date and are recognized in the statement of operations over the requisite service period. When the requisite service period precedes the grant date and a market condition exists in the warrant, the Company values the warrant using the Monte Carlo Simulation Method. When the terms of the warrant become fixed, the Company values the warrant using the Black-Scholes Option Pricing Method. As allowed by ASC 718 for companies with a short period of publicly traded stock history, the Company’s estimate of expected volatility is based on the average volatilities of a sampling of eight to nine companies with similar attributes to the Company, including industry, stage of life cycle, size and financial leverage. The risk-free rate for periods within the contractual life of the warrant is based on the U.S. Treasury yield curve in effect at the time of grant valuation. In determining the value of the warrant until the terms are fixed, the Company factors in the probability of the market condition occurring and several possible scenarios. When the requisite service period precedes the grant date and is deemed to be complete, the Company records the fair value of the warrant at the time of issuance as an equity stock-based compensation transaction. The grant date is determined when all pertinent information, such as exercise price and quantity are known. Restricted stock units: The restricted stock units, or RSUs, are valued on the grant date and the fair value of the RSUs is equal to the market price of the Company’s common stock on the grant date. The RSU expense is recognized over the requisite service period. When the requisite service period begins prior to the grant date (because the service inception date occurs prior to the grant date), the Company is required to begin recognizing compensation cost before there is a measurement date (i.e., the grant date). The service inception date is the beginning of the requisite service period. If the service inception date precedes the grant date, accrual of compensation cost for periods before the grant date shall be based on the fair value of the award at the reporting date. In the period in which the grant date occurs, cumulative compensation cost shall be adjusted to reflect the cumulative effect of measuring compensation cost based on fair value at the grant date rather than the fair value previously used at the service inception date (or any subsequent reporting date).
Income Taxes	Income Taxes: The Company follows Income Taxes , The standard A On December 22, 2017, H.R. 1/Public Law No. 115-97 known as the Tax Cuts and Jobs Act (the “Tax Act”), was signed into law. The effects of this new federal legislation are recognized upon enactment, which is the date a bill is signed into law. The Act includes numerous changes in existing tax law, including a permanent reduction in the federal corporate income tax rate from 35% (as the top corporate tax rate) to 21%. As a result of the Tax Act, the Company has revalued its net deferred tax assets as of December 31, 2017 to reflect the rate reduction. Pursuant to the SEC Staff Accounting Bulletin ("SAB") No. 118, "Income Tax Accounting Implications of the Tax Cuts and Jobs Act" ("SAB 118"), a company may select between one of three scenarios to determine a reasonable estimate arising from the Tax Act. Those scenarios are (i) a final estimate which effectively closes the measurement window; (ii) a reasonable estimate leaving the measurement window open for future revisions; and (iii) no estimate as the law is still being analyzed. The Company was able to provide a reasonable estimate for the revaluation of deferred taxes by recording a net tax provision of $141.1 million in the period ending December 31, 2017, which is offset by a full valuation allowance. Other impacts of the Act including, but not limited to, a limitation of the deduction for net operating losses, additional limitations on the deductibility of executive compensation
Segment Reporting	Segment Reporting: Management has determined that the Company operates in one business segment which is the development and commercialization of innovative products to enhance cancer care.
Net Loss per Common Share	Net Loss per Common Share: Basic net loss per common share is computed by dividing net loss applicable to common stockholders by the weighted average number of common shares outstanding during the periods presented as required by ASC 260, Earnings per Share
Recently Issued Accounting Standards	Recently Issued Accounting Standards: In May 2014, the Financial Accounting Standards Board (“FASB”), issued a new accounting standard that amends the guidance for the recognition of revenue from contracts with customers to transfer goods and services. The FASB has subsequently issued additional, clarifying standards to address issues arising from implementation of the new revenue recognition standard. The new revenue recognition standard and clarifying standards are effective for interim and annual periods beginning on January 1, 2018, but could have been adopted early beginning January 1, 2017. The Company has chosen to adopt this standard as of January 1, 2017 as it began to generate revenue, with no revenue recognized in prior years. The Company has also identified and implemented changes to its accounting policies, business processes, and internal controls to support the new accounting and disclosure requirements. In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities In February 2016, the FASB issued Accounting Standards Update, or ASU, No. 2016-02, Leases In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation: Improvements to Employee Share-Based Payment Accounting, which was intended to simplify various aspects of accounting for share-based payment transactions. The new guidance requires immediate recognition of all excess tax benefits and deficiencies in the income statement; requires classification of excess tax benefits as an operating activity as opposed to a financing activity in the statements of cash flows; requires the classification of cash paid by an employer when directly withholding shares for tax-withholding purposes be classified as a financing activity on the statements of cash flows; and allows the Company to make an accounting policy election to either estimate the number of awards expected to vest or account for forfeitures when they occur. The standard is effective for annual reporting periods beginning after December 15, 2016, and interim periods within those annual reporting periods. The Company applied an accounting policy election to estimate forfeitures and then true up actual forfeitures as they occur. Because this treatment was in line with the Company’s current treatment of forfeitures, the impact was insignificant as of December 31, 2017. This adoption resulted in a one-time net increase to the net operating losses deferred tax asset and the corresponding valuation allowance of $184.1 million at the federal and state level, which is a primarily cumulative adjustment for the previously unrecognized windfall tax benefits related to previous vesting and exercises of stock-based awards. The Company applied this standard in the first quarter of 2017 using the modified retrospective transition method of adoption. Due to the full valuation allowance on the deferred tax assets, the adoption did not have any impact on the Company’s consolidated financial statements on the adoption date. In addition, under the new standard, the Company will prospectively reflect the tax deficiencies and benefits as an operating activity, rather than as a financing activity under the previous standard, in the Company’s Consolidated Statements of Cash Flows. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows Topic 230 : Classification of Certain Cash Receipts and Cash Payments a consensus of the Emerging Issues Task Force In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows Topic 230 Restricted Cash In July 2015, the FASB issued ASU 2015-11, Inventory (Topic 330) Simplifying the Measurement of Inventory

Significant Accounting Polici23

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Product Revenues from Each Customer	Product revenue from each of our customers who individually accounted for 10% or more of total revenues consisted of the following: December 31, 2017 Customer A 38 % Customer B 23 % Customer C 13 %
Assets Measured at Fair Value on Recurring Basis	Following are the major categories of assets measured at fair value on a recurring basis as of December 31, 2017 and 2016, using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3) (in thousands): December 31, 2017 Level 1 Level 2 Level 3 Total Cash equivalents $ 81,698 $ — $ — $ 81,698 $ 81,698 $ — $ — $ 81,698 December 31, 2016 Level 1 Level 2 Level 3 Total Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper — 5,998 — 5,998 Marketable securities - corporate bonds — 28,984 — 28,984 $ 188,543 $ 34,982 $ — $ 223,525
Summary of Short-term Investments	The following tables summarize the Company’s short-term investments (in thousands): Maturity Amortized Unrealized Estimated December 31, 2017 (in years) cost Gains Losses fair value Cash equivalents $ 81,698 $ — $ — $ 81,698 $ 81,698 $ — $ — $ 81,698 Maturity Amortized Unrealized Estimated December 31, 2016 (in years) cost Gains Losses fair value Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper Less than 1 5,998 — — 5,998 Marketable securities - corporate bonds Less than 1 28,997 — (13 ) 28,984 $ 223,538 $ — $ (13 ) $ 223,525

Prepaid Expenses and Other (Tab

Prepaid Expenses and Other (Tables)	12 Months Ended
	Dec. 31, 2017
Banking And Thrift [Abstract]
Components of Prepaid Expenses and Other	Prepaid expenses and other consisted of the following at December 31 (in thousands): December 31, 2017 December 31, 2016 Current: CRO services $ 7,188 $ 3,471 Other clinical development 878 1,069 Insurance 1,306 1,159 Other 3,625 1,299 12,997 6,998 Long-term: CRO services 860 5,077 Other clinical development 886 1,243 Insurance 26 40 Other 217 486 1,989 6,846 Totals $ 14,986 $ 13,844

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Property and Equipment	Property and equipment consisted of the following at December 31 (in thousands): Property and Equipment: December 31, 2017 December 31, 2016 Leasehold improvements $ 3,878 $ 3,878 Computer equipment 2,147 1,822 Telephone equipment 302 256 Furniture and fixtures 2,206 2,146 8,533 8,102 Less: accumulated depreciation and amortization (4,063 ) (2,949 ) Totals $ 4,470 $ 5,153

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Intangible assets	Intangible assets consisted of the following at December 31 (in thousands): December 31, 2017 Estimated useful life Acquired and in-licensed rights $ 50,000 13 Years Less: accumulated amortization (1,645 ) Total intangible asset, net $ 48,355
Schedule of Estimated Future Intangible Amortization Expense	Estimated future intangible amortization expense as of December 31, 2017 is as follows (in thousands): 2018 $ 3,947 2019 3,947 2020 3,947 2021 3,947 2022 3,947 Thereafter 28,620 Total $ 48,355

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2017
Payables And Accruals [Abstract]
Accrued Expenses	Accrued expenses consisted of the following at December 31 (in thousands): December 31, 2017 December 31, 2016 Accrued CRO services $ 8,335 $ 6,609 Accrued other clinical development 3,438 7,015 Accrued legal fees 2,046 706 Accrued compensation 2,797 1,986 Accrued bonus 3,376 1,072 Accrued royalties 3,922 — Other 6,734 38 Totals $ 30,648 $ 17,426

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Long Term Debt	Long term debt consisted of the following at December 31, 2017 (in thousands): Twelve Months Ended Maturity Date Long term debt $ 50,000 October 31, 2022 Less: deferred financing costs (1,523 ) Total long term debt, net $ 48,477

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Fair Value Options Weighted-Average Assumptions	The fair value of options granted to employees was estimated using the Black-Scholes Option Pricing Method (see Note 2) with the following weighted-average assumptions used during the years ended December 31: 2017 2016 Dividend yield 0.0 % 0.0 % Expected volatility 70.2 % 68.1 % Risk-free interest rate 2.0 % 1.7 % Expected life in years 5.83 5.80
Employee Stock-based Compensation	Employee stock-based compensation was as follows for the years ended December 31 (in thousands except per share data): Twelve Months Ended December 31, 2017 2016 2015 Stock-based compensation: Options - Research and development, or R&D $ 67,299 $ 88,049 $ 76,995 Selling, general and administrative, or SG&A 23,024 25,043 17,166 Performance shares - R&D — (528 ) 773 Restricted stock units - Selling, general and administrative, or SG&A 8,170 1,580 — Research and development, or R&D 10,242 3,120 — Total stock-based compensation expense $ 108,735 $ 117,264 $ 94,934
Activity with Respect to Options Granted	Activity with respect to options granted under the 2011 and 2017 Plan is summarized as follows: Shares Weighted Average Exercise Price Weighted Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2014 3,978,126 $ 89.55 8.7 $ 431,635 Granted 2,606,183 $ 117.62 9.4 — Forfeited (277,140 ) $ 177.98 — — Exercised (757,038 ) $ 36.19 — $ 102,149 Expired (7,846 ) $ 105.42 Outstanding at December 31, 2015 5,542,285 $ 105.59 8.6 $ 87,632 Granted 1,658,465 $ 42.34 9.3 Forfeited (446,544 ) $ 122.50 Exercised (43,751 ) $ 13.16 $ 1,360 Expired (131,933 ) $ 185.10 Outstanding at December 31, 2016 6,578,522 $ 87.52 8.0 $ 18,442 Granted 519,791 $ 38.87 8.4 Forfeited (285,377 ) $ 50.11 Exercised (557,080 ) $ 48.71 $ 27,185 Expired (121,343 ) $ 125.40 Outstanding at December 31, 2017 6,134,513 $ 87.91 7.2 $ 220,060 Nonvested at December 31, 2017 1,788,436 $ 55.52 8.6 $ 82,445 Exercisable at December 31, 2017 4,346,077 $ 101.24 6.6 $ 137,615
Stock Options	The weighted-average grant date fair value of options granted during the years ended December 31, 2017, 2016 and 2015, was $24.30, $25.69 and $68.30 per share, respectively. Weighted Average Grant-Date Stock options Shares Fair Value Nonvested shares at December 31, 2015 3,572,202 $ 73.59 Granted 1,658,465 25.69 Vested/Issued (1,678,040 ) 77.69 Forfeited (446,544 ) 73.22 Nonvested shares at December 31, 2016 3,106,083 47.78 Granted 519,791 24.30 Vested/Issued (1,552,061 ) 59.76 Forfeited (285,377 ) 30.21 Nonvested shares at December 31, 2017 1,788,436 $ 33.37
Restricted Stock Units	The weighted average grant date fair value of restricted stock units awarded during the year ended December 31, 2017 was $94.93. Weighted Average Grant-Date Restricted stock units Shares Fair Value Nonvested shares at December 31, 2015 - $ - Granted 640,644 54.35 Vested/Issued (2,917 ) 54.35 Forfeited (7,219 ) 54.35 Nonvested shares at December 31, 2016 630,508 54.35 Granted 1,277,081 94.93 Vested/Issued (211,761 ) 55.17 Forfeited (58,166 ) 63.02 Nonvested shares at December 31, 2017 1,637,662 $ 85.58

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Components of Net Deferred Tax Assets	The components 2017 2016 Deferred tax assets—2017: Net operating loss carry forwards $ 257,121 $ 209,308 Business credit carryforwards 29,695 21,256 Organization costs 180 177 Compensation 76,423 84,341 Deferred rent - leasehold improvement 680 1,194 Other 806 997 364,905 317,273 Deferred tax liabilities (758 ) (1,269 ) Total deferred tax assets 364,147 316,004 Valuation allowance (364,147 ) (316,004 ) Net deferred tax assets $ — $ —
Schedule of Income Tax Reconciliation	The provision 2017 2016 2015 Tax computed at the federal statutory rate $ (99,234 ) $ (93,839 ) $ (81,356 ) State taxes (15,890 ) (15,693 ) (16,620 ) Permanent items (1,404 ) 6,152 4,225 R&D credits (6,217 ) (2,728 ) (5,029 ) Deferred tax asset adjustment 6,805 — — Other (20 ) (113 ) (2,571 ) Impact of federal statutory rate change related to the 2017 Tax Act 141,147 — — Change in valuation allowance (25,187 ) 106,221 101,351 Total provision $ — $ — $ —
Reconciliation of Unrecognized Tax Benefits	The following is a tabular reconciliation of the total amounts of unrecognized tax benefits at December 31:. (in thousands) 2017 2016 2015 Unrecognized tax benefits—January 1 $ 5,315 $ 4,475 $ 2,482 Gross decreases—tax positions in prior period — — — Gross increases—tax positions in current period 1,836 840 1,993 Unrecognized tax benefits—December 31 $ 7,151 $ 5,315 $ 4,475

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Lease Payments	Future minimum lease payments for each of the years subsequent to December 31, 2017, are as follows (in thousands): Year Ending December 31, Amount 2018 $ 4,472 2019 4,859 2020 5,141 2021 5,300 Thereafter 24,090 Total $ 43,862
Summary of Clinical Research Organization Contracts	The contracts also contain variable costs that are hard to predict as they are based on such things as patients enrolled and clinical trial sites, which can vary and therefore, are not included in the table below. The contracts held by the Company as of December 31, 2017, are summarized as follows (in thousands): Indication Estimated Contractual Obligation as of December 31, 2017 Months Remaining on Contract HER2 Overexpressed/Amplified Breast Cancer (Extension) $ 20,323 24 HER2 Overexpressed/Amplified Breast Cancer (Licensor Legacy Clinical Trials) 1,137 12 HER2 Mutated Non-Small Cell Lung Cancer 185 12 HER2 Mutated Breast Cancer and HER2 Mutated Breast Cancer with Brain Mets 5,478 23 Metastatic & Adjuvant Breast Cancer 34,982 32 Neoadjuvant Breast Cancer 3,636 12 Preclinical Research 20,150 40 HER2 Mutated Solid Tumors 10,359 24 Other 20,736 24 Total $ 116,986

Quarterly Financial Data (Table

Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	Quarterly financial data (in thousands except share and per share data): (unaudited) Three Months Ended March 31, June 30, September 30, December 31, 2017 Revenues $ — $ — $ 6,077 $ 21,608 Net loss 72,865 77,832 77,180 64,078 Net loss attributable to common stock 72,865 77,832 77,180 64,078 Net loss per share—basic and diluted $ 1.97 $ 2.10 $ 2.07 $ 1.71 Weighted-average common shares outstanding—basic and diluted 36,931,167 36,992,017 37,214,002 37,534,410 2016 Revenues $ — $ — $ — $ — Net loss (70,972 ) (66,597 ) (65,781 ) (72,661 ) Net loss attributable to common stock (70,972 ) (66,597 ) (65,781 ) (72,661 ) Net loss per share—basic and diluted $ (2.19 ) $ (2.05 ) $ (2.02 ) $ (2.04 ) Weighted-average common shares outstanding—basic and diluted 32,478,408 32,493,092 32,497,168 35,694,193 2015 Revenues $ — $ — $ — $ — Net loss (52,454 ) (64,694 ) (60,417 ) (61,719 ) Net loss attributable to common stock (52,454 ) (64,694 ) (60,417 ) (61,719 ) Net loss per share—basic and diluted $ (1.66 ) $ (2.01 ) $ (1.87 ) $ (1.90 ) Weighted-average common shares outstanding—basic and diluted 31,588,315 32,158,108 32,303,203 32,444,270

Business and Basis of Present33

Business and Basis of Presentation - Additional Information (Detail) - USD ($)	Oct. 20, 2016	Oct. 31, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 31, 2017
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net loss			$ 64,078,000	$ 77,180,000	$ 77,832,000	$ 72,865,000	$ (72,661,000)	$ (65,781,000)	$ (66,597,000)	$ (70,972,000)	$ (61,719,000)	$ (60,417,000)	$ (64,694,000)	$ (52,454,000)	$ (291,955,000)	$ (276,011,000)	$ (239,284,000)
Net cash used in operating activities															(172,470,000)	(141,690,000)	(154,468,000)
Cash and cash equivalents and marketable securities			$ 81,700,000												$ 81,700,000
Net proceeds from issuance of common stock																$ 161,854,000	$ 205,133,000
Silicon Valley Bank and Oxford finance | Term Loan
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Term loan, maximum borrowing capacity																		$ 100,000,000
Underwritten Public Offering
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net proceeds from issuance of common stock	$ 161,900,000	$ 161,900,000

Significant Accounting Polici34

Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017USD ($)Segmentshares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015shares
Significant Accounting Policies [Line Items]
Amortization expenses related to intangible assets		$ 1,600,000
Estimated future amortization expense related to intangible assets, 2018		3,947,000
Estimated future amortization expense related to intangible assets, 2019		3,947,000
Estimated future amortization expense related to intangible assets, 2020		3,947,000
Estimated future amortization expense related to intangible assets, 2021		3,947,000
Estimated future amortization expense related to intangible assets, 2022		3,900,000
Estimated future amortization expense related to intangible assets, 2023		3,900,000
Estimated future amortization expense related to intangible assets, 2024		3,900,000
Estimated future amortization expense related to intangible assets, 2025		3,900,000
Estimated future amortization expense related to intangible assets, 2026		3,900,000
Estimated future amortization expense related to intangible assets, 2027		3,900,000
Estimated future amortization expense related to intangible assets, 2028		3,900,000
Estimated future amortization expense related to intangible assets, 2029		3,900,000
Estimated future amortization expense related to intangible assets, 2030		1,000,000
Incremental costs expenses		0
Cash and cash equivalents in excess of insured limits		$ 86,700,000
Reserve for research and development (“R&D”) credit carryover balance		20.00%
Federal corporate income tax rate		35.00%
Provisional tax impact related to the revaluation of deferred tax assets		$ 141,100,000
Number of segments | Segment		1
Anti-dilutive securities excluded from the calculation of diluted earnings per share | shares			9,325,381	7,668,007
Revenue recognized in prior year			$ 0
One-time net increase in stock-based award expense due to Tax Reform, net of tax		$ 184,100,000
Restricted Stock Units
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share | shares		1,637,662
Warrants
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share | shares		2,116,250
Employee Stock Option
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share | shares		6,134,513
Scenario, Forecast
Significant Accounting Policies [Line Items]
Federal corporate income tax rate	21.00%
Minimum
Significant Accounting Policies [Line Items]
Revenue recognition, payment terms		10 days
Maximum
Significant Accounting Policies [Line Items]
Revenue recognition, payment terms		60 days
Amortization period recognized		1 year

Summary of Product Revenues fro

Summary of Product Revenues from Each Customer (Detail) - Customer Concentration Risk - Sales Revenue, Net	12 Months Ended
	Dec. 31, 2017
Customer A
Significant Accounting Policies [Line Items]
Concentration risk percentage	38.00%
Customer B
Significant Accounting Policies [Line Items]
Concentration risk percentage	23.00%
Customer C
Significant Accounting Policies [Line Items]
Concentration risk percentage	13.00%

Assets Measured at Fair Value o

Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 81,698	$ 188,543
Total	81,698	223,525
Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		5,998
Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		28,984
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	81,698	188,543
Total	$ 81,698	188,543
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total		34,982
Level 2 | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		5,998
Level 2 | Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		$ 28,984

Summary of Short-term Investmen

Summary of Short-term Investments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 223,538	$ 81,698
Unrealized Losses	(13)
Estimated fair value	223,525	81,698
Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	188,543	81,698
Estimated fair value	$ 188,543	$ 81,698
Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Maturity (in years)	Less than 1
Amortized cost	$ 5,998
Estimated fair value	$ 5,998
Corporate bonds
Schedule Of Available For Sale Securities [Line Items]
Maturity (in years)	Less than 1
Amortized cost	$ 28,997
Unrealized Losses	(13)
Estimated fair value	$ 28,984

Components of Prepaid Expenses

Components of Prepaid Expenses and Other (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	$ 12,997	$ 6,998
Prepaid expenses and other, long-term	1,989	6,846
Totals	14,986	13,844
CRO services
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	7,188	3,471
Prepaid expenses and other, long-term	860	5,077
Other clinical development
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	878	1,069
Prepaid expenses and other, long-term	886	1,243
Insurance
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	1,306	1,159
Prepaid expenses and other, long-term	26	40
Other
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	3,625	1,299
Prepaid expenses and other, long-term	$ 217	$ 486

Property and Equipment (Detail)

Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 8,533	$ 8,102
Less: accumulated depreciation and amortization	(4,063)	(2,949)
Totals	4,470	5,153
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	3,878	3,878
Computer Equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	2,147	1,822
Telephone Equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	302	256
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 2,206	$ 2,146

Schedule of Intangible assets (

Schedule of Intangible assets (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Finite Lived Intangible Assets [Line Items]
Acquired and in-licensed rights	$ 50,000
Less: accumulated amortization	(1,645)
Total intangible asset, net	$ 48,355
Acquired and in-licensed rights
Finite Lived Intangible Assets [Line Items]
Estimated useful life	13 years

Schedule of Estimated Future In

Schedule of Estimated Future Intangible Amortization Expense (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Finite Lived Intangible Assets Future Amortization Expense [Abstract]
2,018	$ 3,947
2,019	3,947
2,020	3,947
2,021	3,947
2,022	3,947
Thereafter	28,620
Total	$ 48,355

Accrued Expenses (Detail)

Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued CRO services	$ 8,335	$ 6,609
Accrued other clinical development	3,438	7,015
Accrued legal fees	2,046	706
Accrued compensation	2,797	1,986
Accrued bonus	3,376	1,072
Accrued royalties	3,922
Other	6,734	38
Totals	$ 30,648	$ 17,426

Debt - Schedule of Long Term De

Debt - Schedule of Long Term Debt (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Debt Disclosure [Abstract]
Long term debt	$ 50,000
Less: deferred financing costs	(1,523)
Total long term debt, net	$ 48,477
Long term debt, maturity date	Oct. 31, 2022

Debt - Additional Information (

Debt - Additional Information (Detail) - Silicon Valley Bank and Oxford finance - Term Loan - USD ($)	Oct. 31, 2017	Dec. 31, 2017
Debt Instrument [Line Items]
Line of credit facility, effective date		Oct. 31, 2017
Line of credit facility, description		the lenders agreed to make term loans available to the Company in an aggregate amount of $100 million, consisting of (i) an aggregate amount of $50 million available on the Effective Date and (ii) an aggregate amount of $50 million available to be drawn at the Company’s option between March 31, 2018 and June 30, 2018, provided the Company has achieved a specified minimum revenue milestone and no event of default is occurring.
Term loan, maximum borrowing capacity	$ 100,000,000
Amount available on effective date under agreement	50,000,000
Line of credit facility available upon achievement of specified minimum revenue milestone	$ 50,000,000
Percentage of issued and outstanding capital stock of its subsidiary pledged	65.00%
Interest rate, description		The term loans under the credit facility bear interest at an annual rate equal to the greater of (i) 7.75% and (ii) the sum of (a) the “prime rate,” as reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue, plus (b) 3.5%. The Company is required to make monthly interest-only payments on each outstanding term loan commencing on the first calendar day of the calendar month following the funding date of such term loan, and continuing on the first calendar day of each calendar month thereafter through December 1, 2019.
Annual interest rate	7.75%
Redemption period start date	Dec. 1, 2019
Line of credit facility closing date	Oct. 31, 2022
Percentage of original principal amount payable in final payment	7.50%
Covenant, description		The credit facility includes affirmative and negative covenants applicable to the Company, its current subsidiary and any subsidiaries it may create in the future. The affirmative covenants include, among others, covenants requiring the Company to maintain its corporate existence and governmental approvals, deliver certain financial reports, maintain insurance coverage and satisfy certain requirements regarding deposit accounts. The Company must also achieve product revenue, measured as of the last day of each fiscal quarter on a trailing three-month basis, that is (i) greater than or equal to 70% of its revenue target set forth in its board-approved projections for the 2017 fiscal year, (ii) greater than or equal to 50% of its revenue target set forth in its board-approved projections for the 2018 fiscal year, and (iii) greater than or equal to 50% of its revenue target set forth in its board-approved projections for the 2019 fiscal year. New minimum revenue levels will be established for each subsequent fiscal year by mutual agreement of the Company, SVB, as administrative agent, and the lenders. The negative covenants include, among others, restrictions on the Company’s transferring collateral, incurring additional indebtedness, engaging in mergers or acquisitions, paying dividends or making other distributions, making investments, creating liens, selling assets and suffering a change in control, in each case subject to certain exceptions.
Credit facility covenants, percentage of target revenue to be achieved for 2017 fiscal year	70.00%
Credit facility covenants, percentage of target revenue to be achieved for 2018 fiscal year	50.00%
Credit facility covenants, percentage of target revenue to be achieved for 2019 fiscal year	50.00%
Percentage of additional interest rate to be charged on the event of default	5.00%
Amount of indebtedness or judgments against company to be considered as threshold limit for default	$ 500,000
First Anniversary of Funding
Debt Instrument [Line Items]
Prepayment fee, percentage	2.00%
Between First Anniversary and Second Anniversary
Debt Instrument [Line Items]
Prepayment fee, percentage	1.00%
Prime Rate
Debt Instrument [Line Items]
Basis spread on variable rate	3.50%

Stockholders Equity - Additiona

Stockholders Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Oct. 20, 2016	Oct. 19, 2016	Oct. 31, 2016	Oct. 31, 2011	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Oct. 04, 2011
Stockholders Equity Note [Line Items]
Common stock, par value					$ 0.0001	$ 0.0001
Issuance of common stock, per share						$ 40	$ 190
Underwriters option exercisable period		30 days
Net proceeds from issuance of common stock						$ 161,854	$ 205,133
Issuance of common stock on exercise of option					557,080	43,751	757,038
Common stock issued upon vesting of restricted stock units					211,761
Common stock, shares authorized					100,000,000	100,000,000
Shares of stock authorized before amendment					110,000,000
Preferred stock, shares authorized					10,000,000
Preferred stock, par value					$ 0.0001
Equity method investment ownership percentage									100.00%
Common stock, shares outstanding					37,594,851	36,826,010
Warrant expiration date					Oct. 4, 2021
Issuance of common stock on exercise of option					6,134,513	6,578,522	5,542,285	3,978,126
Share based compensation awarded					519,791	1,658,465	2,606,183
Weighted-average grant date fair value of options granted					$ 24.30	$ 25.69	$ 68.30
Non Vested Stock Options
Stockholders Equity Note [Line Items]
Estimated unrecognized employee compensation cost related to non-vested stock options granted					$ 51,300
Estimated unrecognized employee compensation cost related to non-vested stock options granted, Weighted-average period of recognition					1 year 3 months 18 days
Restricted Stock Units
Stockholders Equity Note [Line Items]
Common stock issued upon vesting of restricted stock units					211,761	2,917
Estimated unrecognized employee compensation cost related to non-vested stock options granted					$ 116,000
Estimated unrecognized employee compensation cost related to non-vested stock options granted, Weighted-average period of recognition						2 years 7 months 6 days
Weighted-average grant date fair value of restricted stock units					$ 94.93	$ 54.35
2011 Plan
Stockholders Equity Note [Line Items]
Common stock shares reserved for issuance					12,529,412
Issuance of common stock on exercise of option					7,538,925
Common stock are available for future issuance					2,643,121
2017 Employment Inducement Incentive Award Plan
Stockholders Equity Note [Line Items]
Common stock shares reserved for issuance					1,000,000
Share based compensation awarded					233,250
Alan Auerbach
Stockholders Equity Note [Line Items]
Percentage of shares held by related party				21.00%
Common Stock
Stockholders Equity Note [Line Items]
Issuance of common stock (in shares)						4,312,500	1,150,000
Issuance of common stock on exercise of option					557,080	46,668	757,038
Common stock, shares outstanding					37,594,851	36,826,010	32,466,842	30,548,309
Shares of common stock that could be acquired by warrant					2,116,250
Common stock price					$ 16
Common Stock | Alan Auerbach
Stockholders Equity Note [Line Items]
Common stock, shares outstanding				18,666,733
Maximum | 2011 Plan
Stockholders Equity Note [Line Items]
Stock options granted, term					10 years
Maximum | 2017 Employment Inducement Incentive Award Plan
Stockholders Equity Note [Line Items]
Stock options granted, term					10 years
Minimum | Common Stock | Alan Auerbach
Stockholders Equity Note [Line Items]
Minimum ownership percentage of outstanding shares of common stock the president need to maintain after issuance of warrants				20.00%
Underwritten Public Offering
Stockholders Equity Note [Line Items]
Issuance of common stock (in shares)		3,750,000
Common stock, par value		$ 0.0001
Issuance of common stock, per share		$ 40
Net proceeds from issuance of common stock	$ 161,900		$ 161,900
Overallotment Option Exercise by Underwriters | Maximum
Stockholders Equity Note [Line Items]
Issuance of common stock (in shares)		562,500

Fair Value Options Weighted-Ave

Fair Value Options Weighted-Average Assumptions (Detail) - Employee Stock Option	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividend yield	0.00%	0.00%
Expected volatility	70.20%	68.10%
Risk-free interest rate	2.00%	1.70%
Expected life in years	5 years 9 months 29 days	5 years 9 months 18 days

Employee Stock-based Compensati

Employee Stock-based Compensation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	$ 108,735	$ 117,264	$ 94,934
Employee Stock Option | Research and development, or R&D
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	67,299	88,049	76,995
Employee Stock Option | Selling, general and administrative, or SG&A
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	23,024	25,043	17,166
Performance Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense		(528)	$ 773
Restricted Stock Units | Research and development, or R&D
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	10,242	3,120
Restricted Stock Units | Selling, general and administrative, or SG&A
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	$ 8,170	$ 1,580

Activity with Respect to Option

Activity with Respect to Options Granted (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Shares
Beginning balance, shares	6,578,522	5,542,285	3,978,126
Granted, shares	519,791	1,658,465	2,606,183
Forfeited, shares	(285,377)	(446,544)	(277,140)
Exercised, shares	(557,080)	(43,751)	(757,038)
Expired, shares	(121,343)	(131,933)	(7,846)
Ending balance, shares	6,134,513	6,578,522	5,542,285	3,978,126
Nonvested, shares	1,788,436	3,106,083	3,572,202
Exercisable, shares	4,346,077
Weighted Average Exercise Price
Beginning Balance, Weighted Average Exercise Price	$ 87.52	$ 105.59	$ 89.55
Granted, Weighted Average Exercise Price	38.87	42.34	117.62
Forfeited, Weighted Average Exercise Price	50.11	122.50	177.98
Exercised, Weighted Average Exercise Price	48.71	13.16	36.19
Expired, Weighted Average Exercise Price	125.40	185.10	105.42
Ending Balance, Weighted Average Exercise Price	87.91	$ 87.52	$ 105.59	$ 89.55
Nonvested, Weighted Average Exercise Price	55.52
Exercisable, Weighted Average Exercise Price	$ 101.24
Weighted Average Remaining Contractual Term (years)
Weighted Average Remaining Contractual Term (years)	7 years 2 months 12 days	8 years	8 years 7 months 6 days	8 years 8 months 12 days
Granted, Weighted Average Remaining Contractual Term (years)	8 years 4 months 24 days	9 years 3 months 18 days	9 years 4 months 24 days
Nonvested, Weighted Average Remaining Contractual Term (years)	8 years 7 months 6 days
Exercisable, Weighted Average Remaining Contractual Term (years)	6 years 7 months 6 days
Aggregate Intrinsic Value
Shares, Outstanding, Aggregate Intrinsic Value	$ 220,060	$ 18,442	$ 87,632	$ 431,635
Exercised, Aggregate Intrinsic Value	27,185	$ 1,360	$ 102,149
Nonvested, Aggregate Intrinsic Value	82,445
Exercisable, Aggregate Intrinsic Value	$ 137,615

Stock Options (Detail)

Stock Options (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares
Nonvested shares, Beginning balance	3,106,083	3,572,202
Granted, shares	519,791	1,658,465	2,606,183
Vested/Issued, shares	(1,552,061)	(1,678,040)
Forfeited, shares	(285,377)	(446,544)
Nonvested shares, Ending balance	1,788,436	3,106,083	3,572,202
Weighted Average Grant-Date Fair Value
Nonvested, Beginning balance, Weighted Average Grant-Date Fair Value	$ 47.78	$ 73.59
Granted, Weighted Average Grant-Date Fair Value	24.30	25.69	$ 68.30
Vested/Issued, Weighted Average Grant-Date Fair Value	59.76	77.69
Forfeited, Weighted Average Grant-Date Fair Value	30.21	73.22
Nonvested, Ending balance, Weighted Average Grant-Date Fair Value	$ 33.37	$ 47.78	$ 73.59

Restricted Stock Units (Detail)

Restricted Stock Units (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Shares
Vested/Issued, shares	(211,761)
Restricted Stock Units
Shares
Nonvested shares, Beginning balance	630,508
Granted, shares	1,277,081	640,644
Vested/Issued, shares	(211,761)	(2,917)
Forfeited, shares	(58,166)	(7,219)
Nonvested shares, Ending balance	1,637,662	630,508
Weighted Average Grant-Date Fair Value
Nonvested, Beginning balance, Weighted Average Grant-Date Fair Value	$ 54.35
Granted, Weighted Average Grant-Date Fair Value	94.93	$ 54.35
Vested/Issued, Weighted Average Grant-Date Fair Value	55.17	54.35
Forfeited, Weighted Average Grant-Date Fair Value	63.02	54.35
Nonvested, Ending balance, Weighted Average Grant-Date Fair Value	$ 85.58	$ 54.35

401(K) Savings Plan - Additiona

401(K) Savings Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution expenses	$ 0.9	$ 1	$ 0.7
First 3% of each Participant's Contributions
Defined Benefit Plan Disclosure [Line Items]
Company's matching contributions to the 401(k)plan	100.00%
Second 2% of each Participant's Contributions
Defined Benefit Plan Disclosure [Line Items]
Company's matching contributions to the 401(k)plan	50.00%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Provision for income taxes	$ 0	$ 0	$ 0
Increase in valuation allowance	$ 48,100,000	$ 106,200,000
Federal operating loss carryforwards, expiration beginning year	2,027
State operating loss carryforwards, expiration beginning year	2,030
Unrecognized tax benefits that would affect the effective tax rate, if recognized	$ 7,200,000
Federal
Income Tax Contingency [Line Items]
Operating loss carryforwards	923,000,000
Federal | Research and development credit carryforwards
Income Tax Contingency [Line Items]
Tax credit carryforwards	$ 19,100,000
Tax credit carryforwards, expiration beginning year	2,032
State
Income Tax Contingency [Line Items]
Operating loss carryforwards	$ 870,000,000
State | Research and development credit carryforwards
Income Tax Contingency [Line Items]
Tax credit carryforwards	$ 13,200,000

Components of Net Deferred Tax

Components of Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets
Net operating loss carry forwards	$ 257,121	$ 209,308
Business credit carryforwards	29,695	21,256
Organization costs	180	177
Compensation	76,423	84,341
Deferred rent - leasehold improvement	680	1,194
Other	806	997
Deferred Tax Assets, Gross, Total	364,905	317,273
Deferred tax liabilities	(758)	(1,269)
Total deferred tax assets	364,147	316,004
Valuation allowance	(364,147)	(316,004)
Net deferred tax assets	$ 0	$ 0

Schedule of Income Tax Reconcil

Schedule of Income Tax Reconciliation (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax computed at the federal statutory rate	$ (99,234,000)	$ (93,839,000)	$ (81,356,000)
State taxes	(15,890,000)	(15,693,000)	(16,620,000)
Permanent items	(1,404,000)	6,152,000	4,225,000
R&D credits	(6,217,000)	(2,728,000)	(5,029,000)
Deferred tax asset adjustment	6,805,000
Other	(20,000)	(113,000)	(2,571,000)
Impact of federal statutory rate change related to the 2017 Tax Act	141,147,000
Change in valuation allowance	(25,187,000)	106,221,000	101,351,000
Total provision	$ 0	$ 0	$ 0

Reconciliation of Unrecognized

Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Unrecognized tax benefits—January 1	$ 5,315	$ 4,475	$ 2,482
Gross increases—tax positions in current period	1,836	840	1,993
Unrecognized tax benefits—December 31	$ 7,151	$ 5,315	$ 4,475

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)

May 02, 2018USD ($)

Apr. 14, 2016DerivativeLawsuit

Apr. 02, 2016USD ($)

Jun. 07, 2012USD ($)

Dec. 07, 2011USD ($)

Oct. 31, 2017ft²

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Jul. 31, 2015ft²

May 19, 2014USD ($)ft²

Mar. 18, 2014USD ($)ft²

Dec. 01, 2013USD ($)ft²

Nov. 28, 2012USD ($)ft²

Commitments And Contingencies Disclosure [Line Items]

Existing square feet of leased property | ft²

9,560

22,775

16,750

13,250

License agreement, expected milestone payment

$ 187,500,000

Company obligations for potential milestone payments for CRO Contracts

$ 22,200,000

Number of shareholders derivative lawsuits | DerivativeLawsuit

2

Los Angeles

Commitments And Contingencies Disclosure [Line Items]

Office lease, lease term

10 years

Additional lease rent per month

$ 150,000

Lease expiration date

Mar. 31, 2026

Additional square feet leased | ft²

14,000

26,000

Lease commencement date

May 1, 2018

Apr. 1, 2016

Percentage of increase in annual rent

3.00%

Los Angeles | Scenario, Forecast

Commitments And Contingencies Disclosure [Line Items]

Office lease, lease term

9 years

Additional lease rent per month

$ 71,000

Percentage of increase in annual rent

3.50%

South San Francisco

Commitments And Contingencies Disclosure [Line Items]

Office lease, lease term

10 years

Additional lease rent per month

$ 51,400

Lease expiration date

Mar. 31, 2026

Additional square feet leased | ft²

13,000

Lease commencement date

Apr. 1, 2016

Percentage of increase in annual rent

3.00%

Additional Office Space Lease

Commitments And Contingencies Disclosure [Line Items]

Additional lease rent per month

$ 22,886

$ 11,487

$ 10,400

$ 12,145

Additional square feet leased | ft²

7,152

2,908

5,949

3,500

Minimum | CRO services

Commitments And Contingencies Disclosure [Line Items]

Written notice of termination, period

30 days

Maximum | CRO services

Commitments And Contingencies Disclosure [Line Items]

Written notice of termination, period

45 days

Maximum | Additional Office Space Lease

Commitments And Contingencies Disclosure [Line Items]

Additional lease rent per month

$ 27,328

$ 12,928

$ 25,100

$ 14,080

Lease Agreement executed on December 7, 2011

Commitments And Contingencies Disclosure [Line Items]

Office lease, lease term

7 years

Lease expiration date

Dec. 9, 2018

Office space, lease extension term

5 years

Office space, lease extension Stand-by letter of credit

$ 2,500,000

Rent expense

$ 3,879,929

$ 3,547,300

$ 1,597,200

Lease Agreement executed on December 7, 2011 | Minimum

Commitments And Contingencies Disclosure [Line Items]

Additional lease rent per month

44,400

Lease Agreement executed on December 7, 2011 | Maximum

Commitments And Contingencies Disclosure [Line Items]

Additional lease rent per month

$ 53,000

Lease Agreement executed on June 7, 2012

Commitments And Contingencies Disclosure [Line Items]

Office lease, lease term

7 years

Office space, lease extension term

5 years

Office space, lease extension Stand-by letter of credit

$ 1,591,400

Lease Agreement executed on June 7, 2012 | Minimum

Commitments And Contingencies Disclosure [Line Items]

Additional lease rent per month

20,250

Lease Agreement executed on June 7, 2012 | Maximum

Commitments And Contingencies Disclosure [Line Items]

Additional lease rent per month

$ 30,820

Future Minimum Lease Payments (

Future Minimum Lease Payments (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Leases [Abstract]
2,018	$ 4,472
2,019	4,859
2,020	5,141
2,021	5,300
Thereafter	24,090
Total	$ 43,862

Summary of Clinical Research Or

Summary of Clinical Research Organization Contracts (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Research And Development Arrangement Contract To Perform For Others [Line Items]
Estimated Contractual Obligations	$ 116,986
HER2 Overexpressed/Amplified Breast Cancer (Extension)
Research And Development Arrangement Contract To Perform For Others [Line Items]
Estimated Contractual Obligations	$ 20,323
Months remaining on contract	24 months
HER2 Overexpressed/Amplified Breast Cancer (Licensor Legacy Clinical Trials)
Research And Development Arrangement Contract To Perform For Others [Line Items]
Estimated Contractual Obligations	$ 1,137
Months remaining on contract	12 months
HER2 Mutated Non-Small Cell Lung Cancer
Research And Development Arrangement Contract To Perform For Others [Line Items]
Estimated Contractual Obligations	$ 185
Months remaining on contract	12 months
HER2 Mutated Breast Cancer and HER2 Mutated Breast Cancer with Brain Mets
Research And Development Arrangement Contract To Perform For Others [Line Items]
Estimated Contractual Obligations	$ 5,478
Months remaining on contract	23 months
Metastatic & Adjuvant Breast Cancer
Research And Development Arrangement Contract To Perform For Others [Line Items]
Estimated Contractual Obligations	$ 34,982
Months remaining on contract	32 months
Neoadjuvant Breast Cancer
Research And Development Arrangement Contract To Perform For Others [Line Items]
Estimated Contractual Obligations	$ 3,636
Months remaining on contract	12 months
Preclinical Research
Research And Development Arrangement Contract To Perform For Others [Line Items]
Estimated Contractual Obligations	$ 20,150
Months remaining on contract	40 months
HER2 Mutated Solid Tumors
Research And Development Arrangement Contract To Perform For Others [Line Items]
Estimated Contractual Obligations	$ 10,359
Months remaining on contract	24 months
Other
Research And Development Arrangement Contract To Perform For Others [Line Items]
Estimated Contractual Obligations	$ 20,736
Months remaining on contract	24 months

Quarterly Financial Data (Detai

Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 21,608	$ 6,077											$ 27,685
Net loss	64,078	77,180	$ 77,832	$ 72,865	$ (72,661)	$ (65,781)	$ (66,597)	$ (70,972)	$ (61,719)	$ (60,417)	$ (64,694)	$ (52,454)	(291,955)	$ (276,011)	$ (239,284)
Net loss attributable to common stock	$ 64,078	$ 77,180	$ 77,832	$ 72,865	$ (72,661)	$ (65,781)	$ (66,597)	$ (70,972)	$ (61,719)	$ (60,417)	$ (64,694)	$ (52,454)	$ (291,955)	$ (276,011)	$ (239,284)
Net loss per share—basic and diluted	$ 1.71	$ 2.07	$ 2.10	$ 1.97	$ (2.04)	$ (2.02)	$ (2.05)	$ (2.19)	$ (1.90)	$ (1.87)	$ (2.01)	$ (1.66)	$ (7.85)	$ (8.29)	$ (7.45)
Weighted-average common shares outstanding—basic and diluted	37,534,410	37,214,002	36,992,017	36,931,167	35,694,193	32,497,168	32,493,092	32,478,408	32,444,270	32,303,203	32,158,108	31,588,315	37,169,678	33,295,114	32,126,094

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($)	Jan. 30, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Company obligations for potential milestone payments for CRO Contracts		$ 22,200,000
Subsequent Event | CANbridge Life Sciences
Subsequent Event [Line Items]
Upfront payment	$ 30,000,000
Minimum | Subsequent Event | CANbridge Life Sciences
Subsequent Event [Line Items]
Company obligations for potential milestone payments for CRO Contracts	40,000,000
Maximum | Subsequent Event | CANbridge Life Sciences
Subsequent Event [Line Items]
Sales-based milestone payments	$ 185,000,000