Molecular Templates (MTEM) 10-K 30 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Mar. 21, 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	MTEM
Entity Registrant Name	MOLECULAR TEMPLATES, INC.
Entity Central Index Key	1,183,765
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Smaller Reporting Company
Entity Public Float			$ 25,999,000
Entity Common Stock, Shares Outstanding		27,058,244

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 58,910	$ 1,716
Prepaid expenses	1,485	120
Other current assets	19	7
Total current assets	60,414	1,843
Property and equipment, net	1,952	334
In-process research and development	26,623	0
Other assets	1,402	921
Total assets	90,391	3,098
Current liabilities:
Accounts payable	2,517	934
Accrued liabilities	2,690	1,210
Current portion of long-term debt	2,400	2,400
Related party debt (Note 8)	0	7,315
Deferred revenue	2,765	1,870
Other current liabilities	70	36
Total current liabilities	10,442	13,765
Warrant liabilities	954	49
Long-term debt, net of current portion	1,078	3,165
Other liabilities	628	53
Total liabilities	13,102	17,032
Commitments and contingencies (Note 10)
Redeemable convertible preferred stock	0	25,871
Stockholders’ equity (deficit):
Common stock, $0.001 par value: Authorized: 150,000,000 shares at December 31, 2017 and 2016; Issued and outstanding: 26,898,330 and 303,303 shares at December 31, 2017 and 2016, respectively	27	0
Additional paid-in capital	141,733	568
Accumulated other comprehensive loss	0	0
Accumulated deficit	(64,471)	(40,373)
Total stockholders’ equity (deficit)	77,289	(39,805)
Total liabilities and stockholders’ equity (deficit)	$ 90,391	$ 3,098

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	26,898,330	214,641
Common stock, shares outstanding	26,898,330	214,641

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Research and development revenue	$ 2,408	$ 0
Grant revenue	987	1,880
Total revenue	3,395	1,880
Operating expenses:
Research and development	9,487	8,017
General and administrative	11,755	4,482
Total operating expenses	21,242	12,499
Loss from operations	(17,847)	(10,619)
Interest and other income, net	51	19
Interest expense	(853)	(431)
Change in fair value of warrant liabilities	128	3
Loss on conversion of notes	(4,619)	0
Net loss	(23,140)	(11,028)
Deemed dividends on preferred stock	(958)	(1,572)
Net loss attributable to common shareholders	$ (24,098)	$ (12,600)
Net loss per share attributable to common shareholders:
Basic and diluted	$ (2.11)	$ (59.04)
Weighted average number of shares used in net loss per share calculations:
Basic and diluted	11,400,881	213,420
Other comprehensive loss:
Unrealized gain (loss) on available-for-sale securities		$ 0
Comprehensive loss	$ (24,098)	$ (12,600)

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($)	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balances, value at Dec. 31, 2015	$ (27,317,000)		$ 0	$ 456,000	$ 0	$ (27,773,000)
Temporary equity, Balances, shares at Dec. 31, 2015		9,116,405
Temporary equity, Balances, value at Dec. 31, 2015		$ 24,299,000
Balances, shares at Dec. 31, 2015			213,128
Issuance of common stock pursuant to stock plans, value	3,000	0	$ 0	3,000	0	0
Issuance of common stock pursuant to stock plans, shares			1,513
Stock-based compensation	109,000	0	$ 0	109,000	0	0
Stock-based compensation, shares			0
Deemed dividends on preferred stock	(1,572,000)	0	$ 0	0	0	(1,572,000)
Temporary equity, Deemed dividends on preferred stock	1,572,000	1,572,000
Unrealized gain (loss) on available-for-sale securities	0	0	0	0	0	0
Net income (loss)	(11,028,000)	$ 0	0	0	0	(11,028,000)
Balances, value at Dec. 31, 2016	(39,805,000)		$ 0	568,000	0	(40,373,000)
Temporary equity, Balances, shares at Dec. 31, 2016		9,116,405
Temporary equity, Balances, value at Dec. 31, 2016	$ 25,871,000	$ 25,871,000
Balances, shares at Dec. 31, 2016	214,641		214,641
Issuance of common stock pursuant to stock plans, value	$ 61,000	$ 0	$ 0	61,000	0	0
Issuance of common stock pursuant to stock plans, shares			17,430
Conversion of preferred stock to common stock in connection with merger	26,829,000		$ 9,000	26,820,000	0	0
Temporary equity, Amount of shares of preferred stock outstanding that were converted to common stock in connection with merger		(9,116,405)
Temporary equity, Conversion of preferred stock to common stock in connection with merger	(26,829,000)	$ (26,829,000)
Conversion of preferred stock to common stock in connection with merger, shares			9,220,478
Conversion of preferred stock warrants to common stock in connection with merger	87,000	0	$ 0	87,000	0	0
Conversion of preferred stock warrants to common stock in connection with merger, shares			12,653
Conversion of redeemable convertible notes to common stock	15,105,000	0	$ 2,000	15,103,000	0	0
Conversion of redeemable convertible notes to common stock, shares			2,208,716
Issuance of common stock and assumption of options in connection with the merger	39,670,000	0	$ 7,000	39,663,000	0	0
Issuance of common stock and assumption of options in connection with the merger, shares			6,508,356
Issuance of common stock to Takeda and certain other investors, net of issuance costs of $2.4 million	57,648,000	0	$ 9,000	57,639,000	0	0
Issuance of common stock to Takeda and certain other investors, net of issuance costs of $2.4 million, shares			8,716,056
Stock-based compensation	1,792,000	0	$ 0	1,792,000	0	0
Stock-based compensation, shares			0
Deemed dividends on preferred stock	(958,000)	0	$ 0	0	0	(958,000)
Temporary equity, Deemed dividends on preferred stock	958,000	958,000
Net income (loss)	(23,140,000)	$ 0	0	0	0	(23,140,000)
Balances, value at Dec. 31, 2017	77,289,000		$ 27,000	$ 141,733,000	$ 0	$ (64,471,000)
Temporary equity, Balances, shares at Dec. 31, 2017		0
Temporary equity, Balances, value at Dec. 31, 2017	$ 0	$ 0
Balances, shares at Dec. 31, 2017	26,898,330		26,898,330

Consolidated Statements of Con6

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Statement Of Stockholders Equity [Abstract]
Issuance of common stock, issuance cost	$ 2.4

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (23,140,000)	$ (11,028,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	155,000	65,000
Stock-based compensation expense	1,792,000	109,000
Amortization of debt discount and accretion related to long term liabilities	342,000	13,000
Change in common stock warrant fair value	(128,000)	(3,000)
Loss on conversion of notes	4,619,000	0
Loss on disposal of equipment	2,000	5,000
Changes in operating assets and liabilities:
Prepaid expenses	(410,000)	0
Other current assets	(12,000)	84,000
Other assets	(81,000)	0
Accounts payable	1,209,000	557,000
Accrued liabilities	155,000	800,000
Other current liabilities	20,000	0
Other liabilities	318,000	0
Deferred revenue	895,000	370,000
Net cash used in operating activities	(14,264,000)	(9,028,000)
Cash flows from investing activities:
Cash received from merger transaction	11,216,000	0
Purchases of property and equipment	(1,101,000)	(101,000)
Increase in other assets	(400,000)	(588,000)
Net cash provided by (used in) investing activities	9,715,000	(689,000)
Cash flows from financing activities:
Payments of capital lease obligations	(43,000)	(44,000)
Proceeds from issuance of long-term debt	0	3,000,000
Repayment of long-term debt	(2,400,000)	(400,000)
Retirement of stock warrants	(208,000)	0
Proceeds from issuance of related party debt	2,685,000	4,630,000
Proceeds from stock option exercise	61,000	2,000
Proceeds from promissory note	4,000,000	0
Proceeds from issuance of common stock and warrants, net of offering expenses	57,648,000	0
Net cash provided by financing activities	61,743,000	7,188,000
Net increase in cash and cash equivalents	57,194,000	(2,529,000)
Cash and cash equivalents, beginning of period	1,716,000	4,245,000
Cash and cash equivalents, end of period	58,910,000	1,716,000
Supplemental Cash Flow Information
Cash paid for interest	250,000	230,000
Non-Cash Investing and Financing Activities
Deemed dividends on preferred stock	958,000	1,573,000
Conversion of preferred stock	26,829,000	0
Conversion of related party debt	10,486,000	0
Conversion of warrant liability	87,000	0
Capital lease additions to fixed assets	291,000	110,000
Fixed asset additions in accounts payable	382,000	20,000
Warrants issued with debt	$ 0	$ 18,000

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE 1—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of the Business Molecular Templates, Inc. (the “Company” or “Molecular”), is clinical stage a biopharmaceutical company formed in 2001, with a biologic therapeutic platform for the development of novel targeted therapeutics for cancer and other diseases, headquartered in Austin, Texas. The Company’s initial focus is on the research and development of therapeutic compounds for a variety of cancers. Molecular operates its business as a single segment, as defined by U.S. generally accepted accounting principles (“U.S. GAAP”). On August 1, 2017, the Company, formerly known as Threshold Pharmaceuticals, Inc. (Nasdaq: THLD) (“Threshold”), completed its business combination with the entity then known as Molecular Templates, Inc., a private Delaware Corporation (“Private Molecular”), in accordance with the terms of an Agreement and Plan of Merger and Reorganization, (the “Merger Agreement”) Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America and include the accounts of the Company and its wholly owned subsidiary, and reflect the elimination of intercompany accounts and transactions. Reverse Stock Split On August 1, 2017, in connection with, and prior to the completion of, the Merger, Threshold effected a Reverse Stock Split Reclassifications Certain amounts in the prior year’s presentations have been reclassified to conform to the current presentation. These reclassifications had no effect on previously reported net loss. Accounting Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America as defined by the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) requires management to make estimates and assumptions that affect certain reported amounts and disclosures. Accordingly, actual results could differ from those estimates. Net Loss per Share Basic net loss per share is calculated by dividing the net loss applicable to common stockholders by the weighted average number of shares of Common Stock outstanding during the period without consideration of Common Stock equivalents. Since the Company was in a loss position for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods, as the inclusion of all potential common shares outstanding is anti-dilutive. Cash and Cash Equivalents The Company considers temporary investments with original maturities of three months or less from date of purchase to be cash equivalents. Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject the Company to concentrations of risk consist principally of cash and cash equivalents, investments, long term debt and accounts receivable. The Company’s cash, cash equivalents are with two major financial institutions in the United States. The Company performs an ongoing credit evaluation of its strategic partners’ financial conditions and generally does not require collateral to secure accounts receivable from its strategic partners. The Company’s exposure to credit risk associated with non-payment will be affected principally by conditions or occurrences within Takeda Pharmaceutical Company Ltd. (“Takeda”). Approximately 56% of total revenues for the year ended December 31, 2017, were derived from Takeda. There were no accounts receivable due from Takeda at December 31, 2017 or 2016. See also Note 4, Research and Development Collaboration Agreements, regarding the collaboration agreements with Takeda. Drug candidates developed by the Company may require approvals or clearances from the FDA or international regulatory agencies prior to commercial sales. There can be no assurance that the Company’s drug candidates will receive any of the required approvals or clearances. If the Company were to be denied approval or clearance or any such approval or clearance were to be delayed, it would have a material adverse impact on the Company. Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Major additions and improvements are capitalized while maintenance and repairs that do not improve or extend the useful life of the respective asset are expensed. Depreciation of property and equipment is computed using the straight-line method over the estimated useful lives of the assets, which range from five to seven years. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful lives of the assets. Impairment of Long-Lived Assets When events, circumstances and/or operating results indicate that the carrying values of long-lived assets might not be recoverable through future operations, the Company prepares projections of the undiscounted future cash flows expected to result from the use of the assets and their eventual disposition. If the projections indicate that the recorded amounts are not expected to be recoverable, such amounts are reduced to estimated fair value. Fair value is estimated based upon internal evaluation of each asset that includes quantitative analyses of net revenue and cash flows, review of recent sales of similar assets and market responses based upon discussions in connection with offers received from potential buyers. Certain factors used for these types of nonrecurring fair value measurements are considered Level 3 inputs. Management determined there was no impairment during the years ended December 31, 2017 and 2016. Revenue Recognition The Company recognizes revenue when persuasive evidence of an arrangement exists, the related services have been performed, the price is fixed and determinable and collectability is reasonably assured. The Company receives funds from a state financial assistance program. The state award is a conditional cost reimbursement grant and revenue is recognized as allowable costs are incurred. Amounts collected in excess of revenue recognized are recorded as deferred revenue. The Company enters into collaboration and option agreements with certain customers. Under the terms of one such agreement, the Company is responsible for providing (i) a license to the Company’s background intellectual property for use in performance of the agreement, and (ii) research and development services. Under ASC 605-25, the agreement is a multiple-element arrangement; under such an arrangement, fixed or determinable contract consideration is allocated to the deliverables with stand-alone value and revenue is recognized for each such deliverable according to the method appropriate for each deliverable. The license to the Company’s background intellectual property for use in performance of the agreement does not have stand-alone value, and thus is combined into one unit of accounting with the research and development services. Revenues are recognized over the period that the research and development services occur. Amounts collected in excess of revenue recognized are recorded as deferred revenue. Income Taxes Income taxes are recorded in accordance with ASC 740, Accounting for Income Taxes (“ASC 740”), which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. The Company determines its deferred tax assets and liabilities based on differences between financial reporting and tax bases of assets and liabilities, which are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Valuation allowances are provided if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. ASC 740 clarifies the accounting for uncertainty in income taxes recognized in the financial statements and provides that a tax benefit from an uncertain tax position may be recognized when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits. This interpretation also provides guidance on measurement, derecognition, classification, interest and penalties, accounting in interim periods and disclosure. The Company’s policy for recording interest and penalties associated with uncertain tax positions is to record such items as a component of tax expense. Stock-Based Compensation The Company accounts for its stock-based compensation awards to employees, including grants of employee stock options, to be recognized in the statements of operations based on their grant date fair values. The Company estimates the grant date fair value of each option award using the Black-Scholes option-pricing model. The use of the Black-Scholes option-pricing model requires management to make assumptions with respect to the expected term of the option, the expected volatility of the common stock consistent with the expected life of the option, risk-free interest rates and expected dividend yields of the common stock. The Company recognizes stock-based compensation expense, equal to the grant date fair value of stock options over the requisite service period. Preferred Stock The Company’s Series A, B and C Convertible Preferred Stock (collectively known as “Preferred Stock”) allowed the holders to require the company to redeem their shares after achievement of specified certain milestones. Certain of the redemption features were outside the Company’s control, and as a result, the Preferred Stock were reflected in the balance sheet as mezzanine equity. Warrants In conjunction with certain financing transactions, the Company issued warrants to purchase the Company’s common stock. The Company determines whether the warrants should be classified as a liability or equity. For warrants classified as liabilities, the Company estimates the fair value of the warrants at each reporting period using Level 3 inputs. The estimates in valuation models are based, in part, on subjective assumptions, including but not limited to stock price volatility, the expected life of the warrants, the risk-free interest rate and the fair value of the common stock underlying the warrants, and could differ materially in the future. The Company will continue to adjust the fair value of the warrant liability at the end of each reporting period for changes in fair value from the prior period until the earlier of the exercise or expiration of the applicable warrant. For warrants classified as equity, the Company records the value of the warrants in additional paid-in capital on the balance sheet. The Company will continue to evaluate the classification of the warrants on a quarterly basis, to determine whether the warrants continue to meet equity classification requirement. Research and Development Costs Research and development expenses consist of costs such as salaries and benefits, laboratory supplies, facility costs, consulting fees and fees paid to contract research organizations, clinical trial sites, laboratories, other clinical service providers and contract manufacturing organizations. Research and development costs are expensed as incurred. In-process Research & Development In-process research and development, or IPR&D, represents the fair value assigned to acquired research and development assets that were not fully developed as of the completion of the Merger. IPR&D acquired in a business combination is capitalized on the Company’s balance sheet at its acquisition-date fair value. Until the project is completed, the asset is accounted for as an indefinite-lived intangible asset subject to impairment testing. Upon completion of a project, the carrying value of the related IPR&D is reclassified to intangible assets and is amortized over the estimated useful life of the asset. The Company evaluates the potential impairment of its intangible assets if events or changes in circumstances indicate that the carrying amount of the asset may not be fully recoverable. Comprehensive loss Comprehensive loss is comprised of the Company’s net loss and other comprehensive income (loss). Unrealized gain (loss) on available-for-sale marketable securities represents the only component of other comprehensive income (loss). Clinical Trial Accruals The Company’s preclinical and clinical trials are performed by third party contract research organizations (CROs) and/or clinical investigators, and clinical supplies are manufactured by contract manufacturing organizations (CMOs). Invoicing from these third parties may be monthly based upon services performed or based upon milestones achieved. The Company accrues these expenses based upon its assessment of the status of each clinical trial and the work completed, and upon information obtained from the CROs and CMOs. The Company’s estimates are dependent upon the timeliness and accuracy of data provided by the CROs and CMOs regarding the status and cost of the studies, and may not match the actual services performed by the organizations. This could result in adjustments to the Company’s research and development expenses in future periods. To date the Company has had no significant adjustments. Bonus Accruals The Company has bonus programs for eligible employees. Bonuses are determined based on various criteria, including the achievement of corporate, departmental and individual goals. Bonus accruals are estimated based on various factors, including target bonus percentages per level of employee and probability of achieving the goals upon which bonuses are based. The Company’s management periodically reviews the progress made towards the goals under the bonus programs. As bonus accruals are dependent upon management’s judgments of the likelihood of achieving the various goals, it is possible for bonus expense to vary significantly in future periods if changes occur in those management estimates. Segments The Company has one reportable segment and uses one measurement of results of operations to manage its business. All long-lived assets are maintained in the United States of America. Recently Issued Accounting Pronouncements In November 2015, the Financial Accounting Standards Board (FASB) issued an accounting standard update for the presentation of deferred income taxes. Under this new guidance, deferred tax liabilities and assets should be classified as noncurrent in a classified balance sheet. The update is effective for the Company beginning in the first quarter of fiscal year 2017 with early adoption permitted as of the beginning of an interim or annual reporting period. Additionally, this guidance may be applied either prospectively or retrospectively to all periods presented. We adopted the standard in the first quarter of 2017 and it did not have a material impact to our consolidated financial statements. In May 2014, the 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. We will adopt the standard using the modified-retrospective approach beginning in 2018. We have completed our assessment of the impact and we do not expect a material impact to total revenue in our consolidated statement of operation and comprehensive loss. We do expect additional disclosures upon the adoption of the standard. In March 2016, the FASB issued an accounting standard update regarding Improvements to Employee – Share Based Payment Accounting that simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The Company adopted the standard effective January 1, 2017 and the adoption did not have a material effect on its consolidated financial statements. In February 2016, the FASB issued a new accounting standard that amends the guidance for the accounting and disclosure of leases. This new standard requires that lessees recognize the assets and liabilities that arise from leases on the balance sheet, including leases classified as operating leases under current GAAP, and disclose qualitative and quantitative information about leasing arrangements. The new standard requires a modified-retrospective approach to adoption and is effective for interim and annual periods beginning on January 1, 2019. The Company is in the process of evaluating the impact the adoption of this standard would have on its financial statements and disclosures. In May 2017, the FASB issued a new accounting standard update on stock compensation and the scope of modification accounting to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. Under this new guidance, modification accounting is required if the fair value, vesting conditions, or classification of the award changes as a result of the change in terms or conditions. The standard is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on its financial statements or disclosures.

Net Income (Loss) Per Common Sh

Net Income (Loss) Per Common Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Income (Loss) Per Common Share	NOTE 2—NET INCOME (LOSS) PER COMMON SHARE Basic net loss per common share is computed by dividing net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per share is computed by giving effect to all potential dilutive common shares, including outstanding options and warrants. The following is the calculation of basic and diluted net loss per share (in thousands, except share and per share data): Years Ended December 31, 2017 2016 Numerator: Net loss attributable to common shareholders $ (24,098 ) $ (12,600 ) Denominator: Weighted-average number of common shares outstanding - basic and diluted 11,400,881 213,420 Net loss per share: Basic and diluted $ (2.11 ) $ (59.04 ) In August 2017, in conjunction with the Merger, all of the Private Molecular common stock was exchanged for the Company’s Common Stock at an exchange ratio of 7.7844, before giving effect to the 11:1 reverse stock split The following outstanding warrants and options were split adjusted, and excluded from the computation of diluted net loss per share for the periods presented because including them would have had an antidilutive effect (in thousands): Years Ended December 31, 2017 2016 Shares issuable upon exercise of warrants 3,332 35 Shares issuable upon exercise of stock options 2,769 942

Merger with Private Molecular

Merger with Private Molecular	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Merger with Private Molecular	NOTE 3— MERGER WITH PRIVATE MOLECULAR On August 1, 2017, the Company, formerly known as Threshold, completed its business combination with Private Molecular, in accordance with the terms of the Merger Agreement Also on August 1, 2017, in connection with, and prior to the completion of, the Merger, Threshold effected an 11-for-1 reverse stock split of its common stock (the “Reverse Stock Split”) and changed its name from Threshold Pharmaceuticals, Inc. to Molecular Templates, Inc. Under the terms of the Merger, at the effective time of the Merger, the Company issued shares of its common stock to Private Molecular stockholders, at an exchange ratio of 7.7844 shares of common stock (the “Exchange Ratio”), before taking into account the Reverse Stock Split, in exchange for each share of Private Molecular common stock outstanding immediately prior to the Merger. Immediately following the closing of the Merger on August 1, 2017, the former Threshold stockholders owned approximately 34.4% of the aggregate number of shares of common stock of the Company and the former Private Molecular stockholders owned approximately 65.6% of the shares of common stock of the Company, subject to adjustments in accordance with the merger agreement. All Private Molecular stock options granted under the 2009 Stock Plan (the “2009 Plan”) (whether or not then exercisable) outstanding prior to the effective time of the Merger were exchanged for options to purchase the Company’s common stock. All outstanding and unexercised Private Molecular stock options assumed by the Company may be exercised solely for shares of the Company’s common stock. The number of shares of the Company’s common stock subject to each Private Molecular stock option assumed by the Company was determined by multiplying (a) the number of shares of Private Molecular common stock that were subject to such Private Molecular stock option, as in effect immediately prior to the effective time of the merger by (b) the Exchange Ratio, then dividing by 11 (to account for the Reverse Stock Split); rounding the resulting number down to the nearest whole number of shares of the Company’s common stock. The per share exercise price for the Company’s common stock issuable upon exercise of each Private Molecular stock option assumed by the Company shall be determined by dividing (a) the per share exercise price of Private Molecular common stock subject to such Private Molecular stock option, as in effect immediately prior to the effective time of the merger, by (b) the Exchange Ratio, then multiplying by 11 (to account for the Reverse Stock Split); rounding the resulting exercise price up to the nearest whole cent. The exchange of the Private Molecular stock options for the Company’s stock options was treated as a modification of the awards. Threshold equity awards issued and outstanding at the time of the Merger remain issued and outstanding. However, for accounting purposes, Threshold equity awards are assumed to have been exchanged for equity awards of Private Molecular, the accounting acquirer. As of August 1, 2017, Threshold had outstanding stock options to purchase 963,681 shares of common stock, of which all were vested and exercisable at a weighted average exercise price of $33.62 per share, after giving effect to the Reverse Stock Split. As all assumed options were fully vested at time of merger, no further stock based compensation expense will be recognized. Allocation of Purchase Consideration Pursuant to business combination accounting, the Company applied the acquisition method, which requires the assets acquired and liabilities assumed be recorded at fair value with limited exceptions. The purchase price for Threshold on August 1, 2017, the closing date of the Merger, was as follows (in thousands, except per share amounts): August 1, 2017 Number of share of the combined company owned by Threshold stockholders 6,508 (1) Multiplied by the price per share of Threshold common stock $ 5.94 (2) Purchase price before options $ 38,658 Threshold options assumed 1,006 (3) Settlement of preexisting bridge note with Threshold (4,010 ) (4) Total purchase price $ 35,654 1. Represents the number of shares of common stock of the combined company that Threshold stockholders owned as of the closing of the Merger pursuant to the Merger Agreement. This amount is calculated as 6,508,356 shares from Threshold common stock outstanding as of August 1, 2017, adjusted for the 11-for-1 reverse stock split. 2. The fair value of Threshold common stock used in determining the purchase price was $5.94, which was derived from the $0.54 per share closing price of Threshold on August 1, 2017, the current price at the time of closing, adjusted for the 11-for-1 reverse stock split. 3. Because Private Molecular is considered to be the acquirer for accounting purposes, the pre-Merger vested stock options granted by Threshold under the 2014 Equity Incentive Plan are deemed to have been exchanged for equity awards of the Company and as such the portion of the acquisition date fair value of these equity awards attributable to pre-Merger service to Threshold were accounted for as a component of the consideration transferred. 4. Represent the bridge loan at the date of merger between Threshold and Molecular. Since the receivable on Threshold’s balance sheet was settled as part of the merger, it is deemed to be a reduction in the purchase price. Under the acquisition method of accounting, the total purchase price was allocated to tangible and identifiable intangible assets acquired and liabilities assumed of Threshold on the basis of their estimated fair values as of the transaction closing date on August 1, 2017. The following table summarizes the allocation of the purchase consideration to the assets acquired and liabilities assumed based on their fair values as of August 1, 2017 (in thousands): August 1, 2017 Cash and cash equivalents $ 11,216 Prepaid expenses and other current assets 945 In-process research and development (IPR&D) 26,623 Accounts payable, accrued expenses (2,009 ) Warrant liability (1,121 ) Net assets acquired $ 35,654 The Company believes that the historical values of Threshold’s current assets and current liabilities approximate fair value based on the short-term nature of such items. The final allocation of the purchase price is dependent on the finalization of the valuation of the fair value of assets acquired and liabilities assumed and may differ from the amounts included in these financial statements. The Company expects to complete the final allocation as soon as practical but no later than one year from the acquisition date. Correction of purchase price and allocation of purchase price During the three months ended December 31, 2017, the Company corrected the purchase price as well as the allocation of the purchase price. In the September 30, 2017 financial statements, the Company originally recorded the settlement of the $4.0 million Threshold bridge loan as a reduction in additional paid-in capital and increase in goodwill. This correction resulted in the elimination of previously recorded goodwill and a reduction in IPR&D of $677,000. The tables above reflect this correction. In Process Research and Development The Company used the risk adjusted discounted cash flow method to value the in-process research and development intangible asset. Under the valuation method, the present value of future cash flows expected to be generated from the in-process research and development of the acquired product candidate, evofosfamide, was determined using a discount rate of 12%, and identified projected cash flows from evofosfamide were risk adjusted to take into consideration the probabilities of moving through the various clinical stages. Transaction Costs Transaction costs associated with the Merger of approximately $2.0 million are included in general and administrative expense. Threshold Promissory Note On March 24, 2017, the Company received $2.0 million from Threshold in the form of a promissory note at an interest rate of 1% per annum. The Company received an additional $2.0 million on June 1, 2017. The note was settled as part of the Merger as a reduction to purchase consideration. Share Based Awards The exchange of Private Molecular stock options to purchase Threshold common stock, as renamed Molecular, was accounted for as a modification of the awards because the legal exchange of the awards is considered a modification of Private Molecular stock options. The modification of the stock options did not result in any incremental compensation expense as the modification did not increase the fair value of the stock options. Options to purchase 963,681 shares of common stock were assumed as a result of the merger. As all assumed options were vested at the time of the merger, no additional stock based compensation will be recognized related to these assumed options. Additionally, pursuant to the terms of the Merger Agreement, participants in the 2014 Equity Incentive Plan received accelerated vesting for all or a portion of their pre-merger awards as well as a modification of the exercise period. The Company recorded $1.2 million in stock compensation associated with the transaction. See Note 13, Equity Incentive Plans and Stock Based Compensation, for further details about stock based compensation recorded. Pro Forma Results in connection with the Merger The Company’s operating results include $320,000 of operating expenses attributable to the former Threshold business activities for the period of August 1, 2017 to December 31, 2017. The unaudited financial information in the following table summarizes the combined results of operations of the Company and Threshold, on a pro forma basis, as if the Merger occurred at the beginning of the periods presented (in thousands, except per share data). Unaudited Years ended December 31, 2017 2016 Revenue $ 6,395 $ 1,880 Net loss $ (15,599 ) $ (35,008 ) The above unaudited pro forma information was determined based on historical GAAP results of Molecular and Threshold. The unaudited pro forma combined results do not necessarily reflect what the Company’s combined results of operations would have been, if the acquisition was completed on January 1, 2016. The unaudited pro forma combined net loss includes pro forma adjustments primarily related to the following non-recurring items directly attributable to the business combinations: • Elimination of combined transaction costs of $5.4 million for the year ended December 31, 2017. No such costs were incurred in 2016. • Elimination of the loss on conversion of notes of $4.6 million for the year ended December 31, 2017. No such loss was incurred in 2016. • Elimination of stock-based compensation expenses of $1.2 million related to the acceleration of vesting and modification of post-termination exercise periods of Threshold stock options awards in connection with the Merger for the year ended December 31, 2017. No such costs were incurred in 2016. • Elimination of severance payments of $2.9 million related to former Threshold executives, in connection with the Merger for the year ended December 31, 2017. No such costs were incurred in 2016. • Elimination of interest expense of $0.3 million and $0.2 million for the years ended December 31, 2017 and 2016, respectively, related to the Threshold bridge loan to Private Molecular that was paid down with the Merger. • Elimination of the change in the fair value of the Threshold warrant liabilities of $0.1 million and $0.1 million of loss for the years ended December 31, 2017 and 2016, respectively.

Research and Development Collab

Research and Development Collaboration Agreements	12 Months Ended
	Dec. 31, 2017
Research And Development [Abstract]
Research and Development Agreements	NOTE 4 — RESEARCH AND DEVELOPMENT AGREEMENTS Related Party Collaboration Agreements - Takeda Pharmaceuticals, Inc. Takeda Collaboration Agreement In October 2016, Private Molecular entered into a collaboration and option agreement (the “Takeda Collaboration Agreement”) with Millennium Pharmaceuticals, Inc., a wholly owned subsidiary of Takeda, to discover and develop CD38-targeting engineered toxin bodies (“ETBs”), which includes MT-4019 for evaluation by Takeda. Under the terms of the Takeda Collaboration Agreement, Molecular is responsible for providing to Takeda (i) new ETBs generated using Takeda’s proprietary fully human antibodies targeting CD38 and (ii) MT-4019 for in vitro and in vivo pharmacological and anti-tumor efficacy evaluations. Molecular granted Takeda (1) a background IP license during the term of the Takeda Collaboration Agreement, and (2) an exclusive option during the term of the Takeda Collaboration Agreement and for a period of thirty days thereafter, to negotiate and obtain an exclusive worldwide license to develop and commercialize any ETB that may result from this collaboration, including MT-4019. Molecular received an upfront payment of $2.0 million in technology access fees and cost reimbursement associated with the Company’s performance and completion of the Company’s obligations under the agreement. The Company determined that the deliverables under the Takeda Collaboration Agreement were the background IP license, as well as the research and development services. The option to license ETBs is a substantive option, and not deemed a deliverable. The Company determined that there was one unit of accounting, since the background IP license did not have standalone value. Revenues are recognized over the period that the research and development services occur using the proportional performance model. During the year ended December 31, 2017, the Company recorded collaboration revenue from Takeda of $1.9 million under the Takeda Collaboration Agreement. During the year ended December 31, 2016, the Company recorded no collaboration revenue from Takeda since no services were performed under the contract. Takeda Multi-Target Agreement In June 2017, Molecular entered into a Multi-Target Collaboration and License Agreement with Takeda (“Takeda Multi-Target Agreement”) in which Molecular will collaborate with Takeda to identify and generate ETBs, against two targets designated by Takeda. Takeda will designate certain targets of interest as the focus of the research. Each party grants to the other nonexclusive rights in its intellectual property for purposes of the conduct of the research, and Molecular agrees to work exclusively with Takeda with respect to the designated targets. Under the Takeda Multi-Target Agreement, Takeda has an option during an option period to obtain an exclusive license under Molecular’s intellectual property to develop, manufacture, commercialize and otherwise exploit ETBs against the designated targets. The option period for each target ends three months after the completion of the evaluation of such designated target. Molecular received an upfront fee of $1.0 million and is entitled to receive an additional $2 million upon the designation of each of the two targets. Molecular may also receive an additional $25.0 million, in aggregate through the exercise of the option to license ETBs. Additionally, Molecular is entitled to receive up to approximately $547.0 million in additional milestone payments through preclinical and clinical development and commercialization. Molecular is also entitled to tiered royalty payments of a mid-single to low-double digit percentage of net sales of any licensed ETBs, subject to certain reductions. The Takeda Multi-Target Agreement will expire on the expiration of the option period (within three months after the completion of the evaluation of each designated target) for the designated targets if Takeda does not exercise its options, or, following exercise of the option, on the later of the expiration of patent rights claiming the licensed ETB or ten years from first commercial sale of a licensed ETB. Takeda Multi-Target Agreement may be sooner terminated by Takeda for convenience or upon a Molecular change of control, or by either party for an uncured material breach of the agreement. The Company determined that the deliverables under the Takeda Multi-Target Agreement were the background IP license, the research and development services, and manufacturing know-how. The option to license ETBs is a substantive option, considered to be at fair value, and not deemed a deliverable. The Company determined that there was one unit of accounting, since the background IP license, and the manufacturing know-how did not have standalone value. Revenues are recognized over the period that the research and development services occur using the proportional performance model. In connection with the execution of the Takeda Multi-Target Agreement. Takeda also entered into a stock purchase agreement with the Company (“Takeda Stock Purchase Agreement”), pursuant to which Takeda purchased approximately $20.0 million of shares of the Company’s common stock following the reverse-merger in the third quarter of 2017. See Note 12. Stockholders’ Equity, for further details. Since the Takeda Stock Purchase Agreement was contingent, it was not a deliverable under the Takeda Multi-Target Agreement. During the year ended December 31, 2017 the Company recorded no collaboration revenue under the Multi-Target Takeda Agreement, since no services had been performed under the project. Other Collaboration Agreements In September 2016, Private Molecular entered into a collaboration agreement an undisclosed pharmaceutical company (“Other Collaboration Agreement”), to generate engineered toxin bodies (“ETBs”), for evaluation. Under the terms of the Other Collaboration Agreement, Molecular is responsible for providing to the customer (i) new ETB generated using the customer’s materials and (ii) ETB study molecules for testing and evaluation. Molecular granted the customer a background IP license during the term of the AbbVie Agreement. This work was completed and accepted in March 2017, and $500,000 was recognized as revenue during the three months ended March 31, 2017. The customer also received an option under the Other Collaboration Agreement for the manufacture of additional quantities of ETB molecules, which they exercised in November 2017. Molecular stands to receive an additional $250,000 under the Other Collaboration Agreement, upon delivery and acceptance of the additional quantities of ETB materials. Grant Agreements The Company receives funds from a state grant funding program, which is a conditional cost reimbursement grant and revenue is recognized as allowable costs are paid. In November 2011, Private Molecular was awarded a $10.6 million product development grant from CPRIT for its CD20-targeting ETB MT-3724. To date, Molecular has received $9.5 million in grant funds. The Company recognized approximately $1.0 million and $1.9 million in grant revenue under these awards during the years ended December 31, 2017 and 2016, respectively. Amounts collected in excess of revenue recognized are recorded as deferred revenue.

Marketable Securities and Fair

Marketable Securities and Fair Value	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Marketable Securities and Fair Value	NOTE 5—MARKETABLE SECURITIES AND FAIR VALUE The Company accounts for its marketable securities in accordance with ASC 820 “Fair Value Measurements and Disclosures.” Level 1 —Quoted prices in active markets for identical assets or liabilities. Level 2 —Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company utilizes the market approach to measure fair value for its financial assets and liabilities. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities. For Level 2 securities that have market prices from multiples sources, a “consensus price” or a weighted average price for each of these securities can be derived from a distribution-curve-based algorithm which includes market prices obtained from a variety of industrial standard data providers (e.g. Bloomberg), security master files from large financial institutions, and other third-party sources. Level 2 securities with short maturities and infrequent secondary market trades are typically priced using mathematical calculations adjusted for observable inputs when available. The following table sets forth the Company’s financial assets (cash equivalents and available-for-sale marketable securities) at fair value on a recurring basis as of December 31, 2017 and 2016: Fair Value as December 31, Basis of Fair Value Measurements (in thousands) 2017 Level 1 Level 2 Level 3 Money market funds $ 51,751 $ 51,751 $ — $ — Fair Value as December 31, Basis of Fair Value Measurements (in thousands) 2016 Level 1 Level 2 Level 3 Money market funds $ 796 $ 796 $ — $ — Refer to Note 12 – Stockholder’s Equity for a table that sets forth the Company’s financial liabilities at fair value on a recurring basis as of December 31, 2017 and 2016. The Company determined the fair value of the liability associated with its 2017 Warrants to purchase in aggregate 377,273 shares of outstanding common stock using a Black-Scholes Model. The Company invests in highly-liquid, investment-grade securities. The following is a summary of the Company’s available-for-sale securities at December 31, 2017 and 2016: As of December 31, 2017 (in thousands): Cost Basis Unrealized Gain Unrealized Loss Fair Value Money market funds $ 51,751 $ — $ — $ 51,751 Less cash equivalents (51,751 ) — — (51,751 ) Total marketable securities $ — $ — $ — $ — As of December 31, 2016 (in thousands): Cost Basis Unrealized Gain Unrealized Loss Fair Value Money market funds $ 796 $ — $ — $ 796 Less cash equivalents (796 ) — — (796 ) Total marketable securities $ — $ — $ — $ — There were no realized gains or losses in years ending December 31, 2017 and 2016 . As of December 31, 2017 and 2016, the fair value of the long-term debt, payable in installments through year ended 2019, approximated its carrying value of $3.5 million and $5.6 million, respectively, because it is carried at a market observable interest rate, which are considered Level 2.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Property and Equipment	NOTE 6—PROPERTY AND EQUIPMENT Property and equipment comprise the following (in thousands): December 31, 2017 2016 Laboratory equipment $ 1,691 $ 488 Leasehold improvements 512 48 Furniture and fixtures 85 32 Computer and equipment 76 35 2,364 603 Less: Accumulated depreciation (412 ) (269 ) Total property and equipment, net $ 1,952 $ 334 Depreciation expense was $155,000 and $65,000 for the years ended December 31, 2017 and 2016, respectively.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Balance Sheet Components	NOTE 7—BALANCE SHEET COMPONENTS Accrued liabilities comprise the following (in thousands): December 31, 2017 2016 Accrued liabilities: General and administrative $ 374 $ 26 Clinical costs 702 409 Non-clinical research 435 2 Bridge note interest — 201 Payroll related 1,149 553 Other accrued expenses 30 19 Total accrued liabilities $ 2,690 $ 1,210 Deferred revenue was comprised of the following: December 31, 2017 2016 Deferred revenue Grant agreements $ 1,673 $ 620 Collaboration agreements 1,092 1,250 Total deferred revenue $ 2,765 $ 1,870

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	NOTE 8 — RELATED PARTY TRANSACTIONS Convertible Notes As of August 1, 2017 and December 31, 2016, the Company had received an aggregate of approximately $10.0 million and $7.3 million, respectively, from stockholders under secured convertible promissory notes (the “Notes”). All of the Notes issued in 2017 and 2016 had the same terms. The Notes were subordinate to the long-term debt due to Silicon Valley Bank (See Note 9. Borrowing Arrangements) and accrue interest at a rate of 5.0% per annum, which was due with all unpaid principal on the maturity date of September 7, 2017. In connection with the Merger, the holders of the Notes agreed to convert the Notes based on an agreed upon price of $3.36 per share and no Notes remain outstanding at December 31, 2017. The principle of $10.0 million and accrued interest $486,900 was converted to 3,121,098 shares, which converted to 2,208,716 post-split shares in the merged entity. As a result, the Company recorded a loss on conversion of notes of $4.6 million during the year ended December 31, 2017, since the agreed upon price was below the fair value of the Notes at the time of the Merger. Takeda Collaboration and Stock Purchase In connection with the Takeda Stock Purchase Agreement described in Note 4. Research and Development Collaboration Agreements, Takeda became a related party, following the stock purchase. Refer to Note 4. Research and Development Collaboration Agreements for more details about the Takeda Collaboration Agreement and the Takeda Multi-Target Agreement. Refer to Note 12. Stockholders’ Equity, for more detail about the Takeda Stock Purchase Agreement. Michael Broxson, a director of the Company is the Vice President and Head of R&D Business Development for Takeda. Concurrent Financing Following the Concurrent Financing described in Note 12 below, Longitude Venture Partner III, L.P. (“Longitude”) and CDK Associates, L.L.C. (“CDK”) became related parties, with Longitude and CDK beneficially owning 15.3% and 5.55% of the Company, respectively, following investments of $20.0 million and $7.0 million, respectively. Scott Morenstein, a director of the Company is a Managing Director of Caxton Alternative Management LP, the investment manager of CDK. David Hirsch, a director of the Company, is a member of Longitude Capital Partners III, LLC, the general partner of Longitude. Furthermore, Kevin Lalande, a director of the Company is affiliated with Sante Health Ventures I, L.P. and Sante Heath Ventures Annex Fund, L.P., which are stockholders of the Company and were investors in the Concurrent Financing. Finally, Excel Venture Fund II, L.P., a stockholder of the Company beneficially owning greater than 5% of the Company invested approximately $333,000 in the Concurrent Financing. Threshold Promissory Note The Company received $4.0 million in the aggregate from Threshold during 2017 in the form on a promissory note that was settled as part of the Merger. Refer to Note 3. Merger with Private Molecular, for more details about the Threshold promissory note.

Borrowing Arrangements

Borrowing Arrangements	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Borrowing Arrangements	NOTE 9 — BORROWING ARRANGEMENTS In April 2014, the Company entered into a loan and security agreement with Silicon Valley Bank (“SVB”) that was subsequently amended in April 2015, to provide for (1) Growth Capital Advances to the Company of up to $6.0 million over three tranches based on corporate milestones (2) term loans of up to $6.0 million in the aggregate (“Growth Capital Loan”); (3) warrants to purchase 14,254 shares of the Company’s common stock at an exercise price of $3.07 per share under the amended loan and security agreement; and (4) a final fee of $345,000 due at the loan maturity date in addition to the principal and interest payments. The Company drew down $0.8 million and $2.3 million in May and June 2015 and issued warrants to purchase 17,310 shares of the Company’s common stock at an exercise price of $3.07 per share under the second and amended loan and security agreement. The Company drew down $3.0 million in April 2016 and issued warrants to purchase 17,310 shares of the Company’s common stock at an exercise price of $3.07 per share under the second term loan. The warrants issued in the Loan Agreement became exercisable upon issuance, and were converted into common stock upon the closing of the Merger. As of December 31, 2017, the Company has received $6 million in the aggregate from this loan and security agreement. The Company is required to repay the outstanding principal in 30 equal installments beginning November 1, 2016 and is due in full on April 30, 2019. Interest accrues at a rate of 1.19% above prime, or 5.44% per annum as of December 31, 2017. Interest only payments were made monthly and beginning November 1, 2016, the Company paid the first of thirty consecutive equal monthly payments of principal plus interest. The Company paid approximately $2.4 million in principal and $237,000 in interest during the year ended December 31, 2017 and $400,000 in principal and $220,000 in interest during the year ended December 31, 2016. The final fee of $345,000 is being accreted to interest expense over the life of the loan using the effective interest method. The Growth Capital Loan matures on April 30, 2019 and is secured by substantially all assets of the Company. The Company does not have any financial loan covenants related to the Growth Capital Loan. As of December 31, 2017 and 2016, the Growth Capital Loan balance was $3.5 million and $5.6 million, respectively. As of December 31, 2017 and 2016, the Company was in compliance with the non-financial covenants of the Growth Capital Loan. Subsequent to December 31, 2017, the Company entered into a term loan facility with Perceptive Credit Holdings II, LP. The Company intends to use the proceeds to pay off the existing arrangement with SVB. Refer to Note 16 – Subsequent events. Future required principal payments on the Growth Capital Loan were as follows as of December 31, 2017 (in thousands): Year Ending December 31, 2018 $ 2,400 2019 1,145 Total 3,545 Debt discount and deferred finance costs (67 ) Total $ 3,478

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 10—COMMITMENTS AND CONTINGENCIES Commitments The Company is obligated under operating lease agreements covering the Company’s office facilities in Austin, Texas and Jersey City, New Jersey, respectively. Facilities expense under the operating leases was approximately $625,000 and $288,000 thousand for the years ended December 31, 2017 and 2016, respectively. Future minimum payments due under the operating lease agreements at December 31, 2017 were as follows (in thousands): Year Ending December 31, 2018 $ 1,003 2019 1,135 2020 1,048 2021 1,074 2022 1,096 Thereafter 486 Total $ 5,842 The Company leases laboratory equipment under non-cancelable capital lease agreements. As of December 31, 2017 and 2016, laboratory equipment under capital leases included in property and equipment totaled approximately $162,000 and $136,000, respectively, net of accumulated amortization of approximately $75,000 and $44,000, respectively. Future minimum capital lease payments consisted of the following at December 31, 2017 (in thousands): Year Ending December 31, 2018 $ 55 2019 33 2020 19 Total future minimum capital lease payments 107 Less amount representing interest (8 ) Total capital lease obligations 99 Current portion of lease obligations (50 ) Capital lease obligations, non-current portion $ 49 Contingencies In the ordinary course of business, the Company may provide indemnifications of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters, including, but not limited to, losses arising out of the Company’s breach of such agreements, services to be provided by or on behalf of the Company, or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with its directors and certain of its officers and employees that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors, officers or employees. The Company maintains director and officer insurance, which may cover certain liabilities arising from its obligation to indemnify its directors and certain of its officers and employees, and former officers and directors in certain circumstances. The Company maintains product liability insurance and comprehensive general liability insurance, which may cover certain liabilities arising from its indemnification obligations. It is not possible to determine the maximum potential amount of exposure under these indemnification obligations due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular indemnification obligation. Such indemnification obligations may not be subject to maximum loss clauses. Management is not currently aware of any matters that could have a material adverse effect on the financial position, results of operations or cash flows of the Company.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2017
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock	NOTE 11 — REDEEMABLE CONVERTIBLE PREFERRED STOCK The following is a summary of the Company’s redeemable convertible preferred stock at December 31, 2017 and 2016 (collectively, the “Preferred Stock”) (in thousands): Shares Issued and Outstanding Par Value Shares Authorized December 31, 2017 December 31, 2016 Series A Preferred Stock $ 0.001 2,500 — 2,500 Series B Preferred Stock $ 0.001 2,273 — 2,273 Series C Preferred Stock $ 0.001 4,392 — 4,343 Total 9,165 — 9,116 On August 1, 2017, the Company’s preferred stock was converted to common shares as a result of the Merger. The outstanding 9,116,405 shares of preferred stock, along with preferred dividends converted to 3,912,892, were converted to 13,029,297 shares of common stock. These common shares were converted upon merger to 9,220,478 shares of the merged entity. Refer to Footnote 3: Merger with Private Molecular, for further details on the Merger. The following table presents changes in the preferred stock during the years ended December 31, 2017 and 2016 (in thousands): Series A Preferred Series B Preferred Series C Preferred Total Balance at December 31, 2015 $ 3,689 $ 5,174 $ 15,436 $ 24,299 Deemed dividends on preferred stock 200 306 1,066 1,572 Balance at December 31, 2016 $ 3,889 $ 5,480 $ 16,502 $ 25,871 Deemed dividends on preferred stock 119 178 661 958 Conversion to common stock in merger (4,008 ) (5,658 ) (17,163 ) (26,829 ) Balance at December 31, 2017 $ — $ — $ — $ —

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	NOTE 12—STOCKHOLDERS’ EQUITY Equity Financings and Related Warrants Concurrent Financing On August 1, 2017, the Company entered into the a securities purchase agreement with Longitude and certain other accredited investors (the “Longitude Securities Purchase Agreement”), pursuant to which the Company sold an aggregate of 5,793,063 units (the “Units”) having an aggregate purchase price of $40.0 million (“PIPE Financing”), each such Unit consisting of (i) one (1) share (the “Shares”) of our common stock and (ii) a warrant (the “Warrants”) to purchase 0.5 shares of our common stock (the “Private Placement”). The Private Placement was pursuant to equity commitment letter agreements entered into by and between the Company and investors in March and June 2017. The purchase price per Unit was $6.9048. The Warrants will be exercisable for a period of seven years from the date of their issuance at a per-share exercise price of $6.8423 (which exercise price shall be payable in cash or through a cashless exercise mechanic), subject to certain adjustments as specified in the Warrants. At December 31, 2017, there were warrants outstanding under this agreement to purchase 2,896,532 share of common stock. The warrants met the requirements for equity classification under ASC 815: Derivatives and Hedging, and the value of these warrants is included in additional paid-in capital on the balance sheet. The warrants are exercisable upon issuance and expire August 1, 2024. In December 2015, the Company entered into an agreement with Wedbush (“Wedbush Agreement”), which was subsequently amended in December of 2017, related to investment banking services. As part of the Wedbush Agreement, the Company issued warrants to purchase 57,930 shares of our common stock. The Warrants will be exercisable for a period of seven years from the date of their issuance at a per-share exercise price of $6.8423 (which exercise price shall be payable in cash or through a cashless exercise mechanic), subject to certain adjustments as specified in the Warrants. The warrants met the requirements for equity classification under ASC 815: Derivatives and Hedging, and the value of these warrants is included in additional paid-in capital on the balance sheet. The warrants are exercisable upon issuance and expire December 1, 2024. Subsequent Financing In connection with the execution of the Takeda Multi-Target Agreement, Threshold and Private Molecular entered into the Takeda Stock Purchase Agreement (“Concurrent Financing”). Pursuant to the Takeda Stock Purchase Agreement, following the consummation of the Merger and Private Placement, Takeda purchased 2,922,993 shares of the Company common stock, at a price per share of $6.8423, for an aggregate purchase price of $20 million. Common Stock Warrant Liability Valuation The Company accounts for certain of its common stock warrants as liabilities under guidance in ASC 480 that clarifies the determination of whether an instrument is classified as a liability or equity. In 2014, 2015 and 2016, the Company issued to SVB warrants to purchase 14,254, 17,310, and 17,310 shares of our common stock, respectively, as part of the SVB loan and securities agreement, with an exercise price of $3.07 per share. Refer to Note 9: Borrowing Arrangements, for further detail about the SVP loan. The SVB warrants were converted into common stock as part of the Merger. Refer to Note 3: Merger with Private Molecular, for further detail about the Merger. On August 1, 2017, as part of the Merger, the Company assumed the warrant liability of the predecessor Threshold, related to issued warrants to purchase 377,273 shares of our common stock, with an exercise price of $39.82 per share. Refer to Note 3: Merger with Private Molecular, for further detail about the Merger. Due to change in control provisions outside of the Company’s control in these warrant agreements, the guidance requires the Company’s outstanding warrants to be classified as liabilities and to be fair valued at each reporting period, with the changes in fair value recognized as other income (expense) in the Company’s consolidated statements of operations. The following table is a reconciliation of the warrant liability measured at fair value using level 3 inputs (in thousands): Warrant Balance at December 31, 2015 34 Initial fair value of common stock warrants 18 Change in fair value of common stock warrants during 2016 (3 ) Balance at December 31, 2016 49 Change in fair value through August 1, 2017 37 Conversion of 2014 warrants to common stock (87 ) Warrant liability related to Merger on August 1, 2017 1,120 Change in fair value during the five months ended December 31, 2017 (165 ) Balance at December 31, 2017 $ 954 At December 31, 2017, the Company had warrants outstanding (“2017 Warrants”) to purchase 377,273 shares of common stock, having an exercise price of $39.82 per share, that were previously issued by Threshold, and which were recorded by Molecular as a liability as part of the Merger transaction. At December 31, 2016, the Company had warrants outstanding (“2014 Warrants”) to purchase 48,874 shares of preferred stock, having an exercise price of $3.07 per share, which were issued by Molecular as part of the loan and security agreement with Silicon Valley Bank (“SVB”). These warrants were converted into common stock at the closing of the Merger. Refer to Note 8, Borrowing Arrangements, for further details about the SVB loan and security agreement. Refer to Note 3 – Merger with Private Molecular. The fair value of these warrants on December 31, 2017 and 2016 was determined using a Black-Scholes model with the following key level 3 inputs: December 31, 2017 December 31, 2016 Risk-free interest rate 1.89 % 1.20 % Expected life (in years) 2.13 2.25 Dividend yield — — Volatility 103 % 76 % Stock price at valuation date $ 10.02 $ 3.07 During the year ended December 31, 2017 the change in fair value of $128,000 of noncash expense related to the warrants was recorded as Change in fair value of warrant liabilities in the Company’s consolidated statement of operations and comprehensive loss. The following table sets forth the Company’s financial liabilities subject to fair value measurements as of December 31, 2017 and 2016 (in thousands): Fair December 31, Basis of Fair Value Measurements (in thousands) 2017 Level 1 Level 2 Level 3 2017 warrants $ 954 $ — $ — $ 954 Fair December 31, Basis of Fair Value Measurements (in thousands) 2016 Level 1 Level 2 Level 3 2014 warrants $ 49 $ — $ — $ 49

Equity Incentive Plans and Stoc

Equity Incentive Plans and Stock Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity Incentive Plans and Stock Based Compensation	NOTE 13—EQUITY INCENTIVE PLANS AND STOCK BASED COMPENSATION 2009 Equity Incentive Plan The 2009 Stock Plan (the “2009 Plan”) provides for the issuance of incentive stock options, nonqualified stock options and restricted stock to employees, directors and consultants of the Company. In August 2017, the Company assumed the 2009 Stock Plan as part of the Merger. The maximum number of shares of common stock that may be issued over the term of the 2009 Plan may not exceed 1,452,268 shares. The Company has reserved a sufficient number of shares of common stock to permit exercise of options in accordance with the terms of the 2009 Plan. The form of the options to be granted under the 2009 Plan will be determined by the Company’s Board of Directors at the time of grant. Options generally vest according to a five-year vesting schedule, with 20% of the shares vesting on the one-year anniversary and equal monthly vesting installments thereafter. As of December 31, 2017, options to purchase 101,667 shares of common stock were available for future grants under the 2009 Plan. 2014 Equity Incentive Plan The terms of the 2014 Equity Incentive Plan (“2014 Plan”) provide for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, other stock awards, and performance awards that may be settled in cash, stock, or other property. Stock options may be granted under the 2014 Plan with an exercise price not less than 100% of the fair market value of the common stock on the date of grant. Stock options under the 2014 Plan may be granted with terms of up to ten years and generally vest over a period of four years, with the exception of grants to non-employee directors and consultants where the vesting period is or may be shorter. As of December 31, 2017, options to purchase 637,029 shares of common stock were available for future grants under the 2014 Plan. 2004 Equity Incentive Plan The 2004 Equity Incentive Plan (“2004 Plan”) provided for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, stock awards and cash awards to employees and consultants. Stock options were granted under the 2004 Plan with an exercise price not less than 100% of the fair market value of the common stock on the date of grant. Stock options under the 2004 Plan were granted with terms of up to ten years and generally vested over a period of four years. The 2004 Plan expired pursuant to its terms on April 7, 2014. No additional awards have been or will be made after April 7, 2014 under the 2004 Plan. 2004 Employee Stock Purchase Plan On January 1, 2017 and 2016 an additional 9,091 shares were authorized for issuance under the 2004 Employee Stock Purchase Plan (“2004 Purchase Plan”) pursuant to the annual automatic increase to the authorized shares under the 2004 Purchase Plan. The 2004 Purchase Plan contains consecutive, overlapping 24 month offering periods. Each offering period includes four six-month purchase periods. The price of the common stock purchased will be the lower of 85% of the fair market value of the common stock at the beginning of an offering period or at the end of the purchase period. For the year ended December 31, 2017, employees had purchased 2,868 shares of common stock under the 2004 Purchase Plan at an average purchase price of $2.80. At December 31, 2017, 18,917 shares were authorized and available for issuance under the 2004 Purchase Plan. For the year ended December 31, 2016, employees had purchased 8,368 shares of common stock under the 2004 Purchase Plan at an average price of $2.75. Threshold equity awards issued and outstanding at the time of the Merger pursuant to the 2004 Plan and the 2014 Plan remain issued and outstanding. However, for accounting purposes, Threshold equity awards are assumed to have been exchanged for equity awards of Private Molecular, the accounting acquirer. The following table summarizes information about stock option activity assuming Threshold equity award plans were assumed by Private Molecular for years ended December 31, 2017 and 2016: Outstanding Weighted Weighted Aggregate Options Average Average Remaining Intrinsic Value Number of Exercise Contractual as of 12/31/2017 Shares Price Term (in millions) Balances, December 31, 2015 922,628 $ 0.89 6.6 $ 0.90 Options granted 31,845 1.85 Options exercised (1,513 ) 1.64 Options canceled (11,276 ) 1.10 Balances, December 31, 2016 941,684 $ 0.92 5.7 $ 0.90 Options assumed in merger (1) 963,681 33.62 Options granted 1,116,627 8.30 Options exercised (17,473 ) 3.66 Options canceled (235,808 ) 35.48 Balances, December 31, 2017 2,768,711 $ 12.07 5.6 $ 11.00 Vested and expected to vest December 31, 2017 2,768,711 $ 12.07 5.6 $ 11.00 Exercisable at December 31, 2017 1,634,268 $ 14.76 2.8 $ 8.90 (1) Private Molecular, as an accounting acquirer assumed stock options covering an aggregate of 963,681 shares of common stock. At December 31, 2017, stock options outstanding and exercisable by exercise price were as follows: Options Outstanding Options Exercisable Range of Exercise Prices Number Outstanding Weighted Average Remaining Contractual Life (Years) Weighted Average Exercise Price Number Exercisable Weighted Average Exercise Price $ 0.42–0.71 480,949 2.14 $ 0.55 480,949 $ 0.55 $ 1.27–1.27 400,412 5.60 $ 1.27 393,560 $ 1.27 $ 1.85–6.05 328,929 4.76 $ 5.26 212,849 $ 5.60 $ 7.14–9.40 1,022,197 9.69 $ 8.64 10,686 $ 7.99 $ 14.30–42.57 277,168 1.53 $ 24.49 277,168 $ 24.49 $ 45.65–85.25 259,056 1.50 $ 59.00 259,056 $ 59.00 $ 0.42–85.25 2,768,711 5.62 $ 12.07 1,634,268 $ 14.76 The total intrinsic value of stock options exercised during the years ended December 31, 2017 and 2016 were $78,000 and $0, respectively, determined at the date of the option exercise. Cash received from stock option exercises were $61,000 and $2,000 for the years ended December 31, 2017 and 2016, respectively. The Company issues new shares of common stock upon exercise of options. In connection with these exercises, there was no tax benefit realized by the Company due to its current loss position. Stock-based Compensation The Company recognizes stock-based compensation in accordance with ASC 718, “Compensation—Stock Compensation.” Years Ended December 31, 2017 2016 Stock-based compensation expense: Research and development $ 340 $ 0 General and administrative 1,452 109 $ 1,792 $ 109 Employee Stock-based Compensation Expense Valuation Assumptions The Company estimated the fair value of stock options granted using the Black-Scholes option-pricing formula and a single option award approach. This fair value is being amortized ratably over the requisite service periods of the awards, which is generally the vesting period. The Company accounts for forfeitures as they occur. The fair value of employee stock options was estimated using the following weighted-average assumptions for the years ended December 31, 2017 and 2016: Years Ended December 31, 2017 2016 Employee Stock Options Risk-free interest rate 2.06 % 1.25 % Expected life (in years) 6.07 5.00 Dividend yield — — Volatility 110 % 76 % Weighted-average fair value of stock options granted $ 6.94 $ 1.31 To determine the expected term of the Company’s employee stock options granted, the Company utilized the simplified approach as defined by SEC Staff Accounting Bulletin No. 107, “Share-Based Payment” The Company recognized $1.8 million and $0.1 million of stock-based compensation expense related to stock options granted under the Company’s equity compensation plans, for the years ended December 31, 2017 and 2016, respectively. Additionally, pursuant to the terms of the Merger Agreement, the participants in the 2014 Equity Incentive Plan received accelerated vesting for all or a portion of their pre-merger awards as well as a modification of the exercise period. The Company recorded $1.2 million in stock compensation associated with the transaction. As of December 31, 2017, the total unrecognized compensation cost related to unvested stock-based awards granted to employees under the Company’s equity compensation plans was approximately $7.1 million. This cost will be recorded as compensation expense ratably over the remaining weighted average requisite service period of approximately 3.5 years.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 14—INCOME TAXES The Tax Reform Act was enacted in December 2017. The Tax Act significantly changes U.S. tax law by, among other things, lowering U.S. corporate income tax rates, implementing a territorial tax system, and imposing a one-time transition tax on deemed repatriated earnings of foreign subsidiaries. The Tax Act reduces the U.S. corporate income tax rate from 35% to 21%, effective January 1, 2018. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to reverse. As a result of the reduction in the U.S. corporate income tax rate from 35% to 21% under the Tax Act, we revalued our ending net deferred tax assets and liabilities at December 31, 2017 and recognized a $6.9 million tax expense that was offset by a change in valuation allowance. The Tax Act provided for a one-time transition tax on the deemed repatriation of post-1986 undistributed foreign subsidiary earnings and profits (“E&P”). The Company currently has one foreign subsidiary that has not commenced operations. As a result, the international aspects of the Tax Act are not applicable. In connection with the initial analysis of the impact of the Tax Act, the Company remeasured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21%. The remeasurement of the Company's deferred tax balance was primarily offset by application of its valuation allowance. The Company is still analyzing certain aspects of the Tax Act and refining its calculations, which could potentially affect the measurement of these balances or potentially give rise to new deferred tax amounts. Where the Company has been able to make reasonable estimates of the effects for which its analysis is not yet complete, the Company has recorded provisional amounts related to the remeasurement of the deferred tax balance. Where the Company has not yet been able to make reasonable estimates of the impact of certain elements, the Company has not recorded any amounts related to those elements and has continued accounting for them in accordance with ASC 740 on the basis of the tax laws in effect immediately prior to the enactment of the Tax Act. For the years ended December 31, 2017 and 2016, the Company did not record an income tax provision due to net operating losses and the inability to record an income tax benefit. A reconciliation of income taxes at the statutory federal income tax rate to net income taxes included in the accompanying statements of operations is as follows (in thousands): 2017 2016 U.S. federal taxes (benefit) at statutory rate $ (7,867 ) $ (3,750 ) State federal income tax benefit (21 ) 10 Permanent differences 87 105 Research and development credits (237 ) (339 ) Change in valuation allowance due to operations 4,766 3,974 Acquisition-related permanent differences 2,281 — Expiring state carryovers and other 991 — Change in valuation allowance due to Tax Act (6,863 ) — U.S. Statutory Rate Change due to Tax Act 6,863 — Total $ — $ — The tax effects of temporary differences that give rise to significant components of the net deferred tax assets are as follows (in thousands): December 31, 2017 2016 Deferred tax assets Net operating loss carryforward $ 13,797 $ 10,446 Research and development credits 5,060 $ 965 Deferred stock compensation 4,058 $ 8 Deferred revenue 581 636 Other 254 9 Total deferred tax assets 23,750 12,064 Total deferred tax liabilities Depreciable and amortizable assets (282 ) (329 ) R&D intangible assets (5,591 ) — Total deferred tax liabilities (5,873 ) (329 ) Less: Valuation allowance (17,877 ) (11,735 ) Net deferred tax assets $ — $ — At December 31, 2017, the Company had federal and state net operating loss carryforwards of approximately $63.2 million and $7.6 million, respectively, available to offset future taxable income. The Company’s federal and state net operating loss carryforwards will begin to expire in 2021 and 2017, respectively, if not used before such time to offset future taxable income or tax liabilities. For federal and state income tax purposes, a portion of the Company’s net operating loss carryforward is subject to certain limitations on annual utilization in case of changes in ownership, as defined by federal and state tax laws. The annual limitation may result in the expiration of the net operating loss before utilization. At December 31, 2017, the Company had federal research and development tax credits of approximately $1.1 million, which expire in the year beginning 2022, and state research and development tax credits of approximately $4.9 million, which have no expiration date. The Company has established a valuation allowance against its deferred tax assets due to the uncertainty surrounding the realization of such assets. The valuation allowance increased by $4.8 million from continuing operations, and the remaining changes in valuation allowance relates to the acquired assets and tax rate changes. The total amount of unrecognized benefits as of December 31, 2017 and 2016 was $1.1 million and $0, respectively. The reconciliation of unrecognized tax benefits at the beginning and end of the year is as follows: (in thousands) 2017 2016 Gross unrecognized tax benefits at January 1, $ — $ — Gross increases (decreases) related to acquisitions 1,064 — Gross increases (decreases) related to current year tax positions 79 — Gross unrecognized tax benefits at December 31, $ 1,143 $ — Included in the balance of unrecognized tax benefits as of December 31, 2017 is $79,000 that is expected to be recognized in the next twelve months and will not affect the Company’s effective tax rate. The Company’s policy is to recognize interest and/or penalties related to income tax matters in income tax expense. As of December 31, 2017 and 2016, the Company had no accrued interest or penalties due to the Company’s net operating losses available to offset any tax adjustment. The Company currently has no federal or state tax examinations in progress nor has it had any federal or state tax examinations since its inception. As a result of the Company’s net operating loss carryforwards, all of its tax years are subject to federal and state tax examination.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plan	NOTE 15—EMPLOYEE BENEFIT PLAN The Company sponsors a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code covering all full-time employees (“Molecular Templates 401(k) Plan”). The Molecular Templates 401(k) Plan is intended to qualify under Section 401 of the Internal Revenue Code. Participants meeting certain criteria, as defined in the plan document, are eligible for a matching contribution, (“Company Match”) in amounts determined at the discretion of the Company. The matching funds become fully vested after three years of service, 25% in year one, 50% in year two, and 100% in year three. Contributions to the Molecular Templates 401(k) Plan by the Company were $0 and $43,000 for the years ended December 31, 2017 and 2016, respectively. As part of the merger on August 1, 2017, the Company assumed Threshold Pharmaceuticals Inc. 401(k) plan, which had been setup to provide a retirement savings program for the former employees of the Threshold Pharmaceuticals, Inc. The 401(k) plan is intended to qualify under Section 401 of the Internal Revenue Code

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	NOTE 16—SUBSEQUENT EVENTS On February 27, 2018, the Company entered into a term loan facility with Perceptive Credit Holdings II, LP (“Perceptive”) in the amount of $10.0 million (“the Credit Facility”). The Credit Facility consists of a $5.0 million term loan, which was drawn on the effective date of the Credit Facility and an additional $5.0 million term loan to be drawn six months following the effective date of the Credit Facility. The Company intends to use the proceeds from the Credit Facility to pay off the existing debt facility with Silicon Valley Bank. Borrowings under the Credit Facility are secured by all of the property and assets of the Company. The principal on the facility accrues interest at an annual rate equal to a three-month LIBOR plus the Applicable Margin. The Applicable Margin will be 11.00%. Upon the occurrence, and during the continuance, of an event of default, the Applicable Margin, defined above, will be increased by 4.00% per annum. The first twenty four months are interest only. After the second anniversary of the closing date of the Credit Facility, the term loans will amortize at $200,000 per calendar quarter. This term loan facility matures on February 27, 2022 and includes both financial and non-financial covenants, including a minimum cash balance requirement. The Company is required to pay an exit fee of $100,000 on a pro rata basis on the maturity date or the earlier date of repayment of the term loans in full. In connection with the Credit Facility, on February 27, 2018 the Company issued Perceptive a warrant to purchase 190,000 shares of the Company’s common stock. The warrant will be exercisable for a period of seven years from the date of issuance at an exercise price of $9.5792, subject to certain adjustments as specified in the Warrant.

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America and include the accounts of the Company and its wholly owned subsidiary, and reflect the elimination of intercompany accounts and transactions.
Reverse Stock Split	Reverse Stock Split On August 1, 2017, in connection with, and prior to the completion of, the Merger, Threshold effected a Reverse Stock Split
Reclassifications	Reclassifications Certain amounts in the prior year’s presentations have been reclassified to conform to the current presentation. These reclassifications had no effect on previously reported net loss.
Accounting Estimates	Accounting Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America as defined by the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) requires management to make estimates and assumptions that affect certain reported amounts and disclosures. Accordingly, actual results could differ from those estimates.
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing the net loss applicable to common stockholders by the weighted average number of shares of Common Stock outstanding during the period without consideration of Common Stock equivalents. Since the Company was in a loss position for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods, as the inclusion of all potential common shares outstanding is anti-dilutive.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers temporary investments with original maturities of three months or less from date of purchase to be cash equivalents.
Concentration of Credit Risk and Other Risks and Uncertainties	Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject the Company to concentrations of risk consist principally of cash and cash equivalents, investments, long term debt and accounts receivable. The Company’s cash, cash equivalents are with two major financial institutions in the United States. The Company performs an ongoing credit evaluation of its strategic partners’ financial conditions and generally does not require collateral to secure accounts receivable from its strategic partners. The Company’s exposure to credit risk associated with non-payment will be affected principally by conditions or occurrences within Takeda Pharmaceutical Company Ltd. (“Takeda”). Approximately 56% of total revenues for the year ended December 31, 2017, were derived from Takeda. There were no accounts receivable due from Takeda at December 31, 2017 or 2016. See also Note 4, Research and Development Collaboration Agreements, regarding the collaboration agreements with Takeda. Drug candidates developed by the Company may require approvals or clearances from the FDA or international regulatory agencies prior to commercial sales. There can be no assurance that the Company’s drug candidates will receive any of the required approvals or clearances. If the Company were to be denied approval or clearance or any such approval or clearance were to be delayed, it would have a material adverse impact on the Company.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Major additions and improvements are capitalized while maintenance and repairs that do not improve or extend the useful life of the respective asset are expensed. Depreciation of property and equipment is computed using the straight-line method over the estimated useful lives of the assets, which range from five to seven years. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful lives of the assets.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets When events, circumstances and/or operating results indicate that the carrying values of long-lived assets might not be recoverable through future operations, the Company prepares projections of the undiscounted future cash flows expected to result from the use of the assets and their eventual disposition. If the projections indicate that the recorded amounts are not expected to be recoverable, such amounts are reduced to estimated fair value. Fair value is estimated based upon internal evaluation of each asset that includes quantitative analyses of net revenue and cash flows, review of recent sales of similar assets and market responses based upon discussions in connection with offers received from potential buyers. Certain factors used for these types of nonrecurring fair value measurements are considered Level 3 inputs. Management determined there was no impairment during the years ended December 31, 2017 and 2016.
Revenue Recognition	Revenue Recognition The Company recognizes revenue when persuasive evidence of an arrangement exists, the related services have been performed, the price is fixed and determinable and collectability is reasonably assured. The Company receives funds from a state financial assistance program. The state award is a conditional cost reimbursement grant and revenue is recognized as allowable costs are incurred. Amounts collected in excess of revenue recognized are recorded as deferred revenue. The Company enters into collaboration and option agreements with certain customers. Under the terms of one such agreement, the Company is responsible for providing (i) a license to the Company’s background intellectual property for use in performance of the agreement, and (ii) research and development services. Under ASC 605-25, the agreement is a multiple-element arrangement; under such an arrangement, fixed or determinable contract consideration is allocated to the deliverables with stand-alone value and revenue is recognized for each such deliverable according to the method appropriate for each deliverable. The license to the Company’s background intellectual property for use in performance of the agreement does not have stand-alone value, and thus is combined into one unit of accounting with the research and development services. Revenues are recognized over the period that the research and development services occur. Amounts collected in excess of revenue recognized are recorded as deferred revenue.
Income Taxes	Income Taxes Income taxes are recorded in accordance with ASC 740, Accounting for Income Taxes (“ASC 740”), which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. The Company determines its deferred tax assets and liabilities based on differences between financial reporting and tax bases of assets and liabilities, which are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Valuation allowances are provided if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. ASC 740 clarifies the accounting for uncertainty in income taxes recognized in the financial statements and provides that a tax benefit from an uncertain tax position may be recognized when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits. This interpretation also provides guidance on measurement, derecognition, classification, interest and penalties, accounting in interim periods and disclosure. The Company’s policy for recording interest and penalties associated with uncertain tax positions is to record such items as a component of tax expense.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for its stock-based compensation awards to employees, including grants of employee stock options, to be recognized in the statements of operations based on their grant date fair values. The Company estimates the grant date fair value of each option award using the Black-Scholes option-pricing model. The use of the Black-Scholes option-pricing model requires management to make assumptions with respect to the expected term of the option, the expected volatility of the common stock consistent with the expected life of the option, risk-free interest rates and expected dividend yields of the common stock. The Company recognizes stock-based compensation expense, equal to the grant date fair value of stock options over the requisite service period.
Preferred Stock	Preferred Stock The Company’s Series A, B and C Convertible Preferred Stock (collectively known as “Preferred Stock”) allowed the holders to require the company to redeem their shares after achievement of specified certain milestones. Certain of the redemption features were outside the Company’s control, and as a result, the Preferred Stock were reflected in the balance sheet as mezzanine equity.
Warrants	Warrants In conjunction with certain financing transactions, the Company issued warrants to purchase the Company’s common stock. The Company determines whether the warrants should be classified as a liability or equity. For warrants classified as liabilities, the Company estimates the fair value of the warrants at each reporting period using Level 3 inputs. The estimates in valuation models are based, in part, on subjective assumptions, including but not limited to stock price volatility, the expected life of the warrants, the risk-free interest rate and the fair value of the common stock underlying the warrants, and could differ materially in the future. The Company will continue to adjust the fair value of the warrant liability at the end of each reporting period for changes in fair value from the prior period until the earlier of the exercise or expiration of the applicable warrant. For warrants classified as equity, the Company records the value of the warrants in additional paid-in capital on the balance sheet. The Company will continue to evaluate the classification of the warrants on a quarterly basis, to determine whether the warrants continue to meet equity classification requirement.
Research and Development Costs	Research and Development Costs Research and development expenses consist of costs such as salaries and benefits, laboratory supplies, facility costs, consulting fees and fees paid to contract research organizations, clinical trial sites, laboratories, other clinical service providers and contract manufacturing organizations. Research and development costs are expensed as incurred.
In-process Research & Development	In-process Research & Development In-process research and development, or IPR&D, represents the fair value assigned to acquired research and development assets that were not fully developed as of the completion of the Merger. IPR&D acquired in a business combination is capitalized on the Company’s balance sheet at its acquisition-date fair value. Until the project is completed, the asset is accounted for as an indefinite-lived intangible asset subject to impairment testing. Upon completion of a project, the carrying value of the related IPR&D is reclassified to intangible assets and is amortized over the estimated useful life of the asset. The Company evaluates the potential impairment of its intangible assets if events or changes in circumstances indicate that the carrying amount of the asset may not be fully recoverable.
Comprehensive Loss	Comprehensive loss Comprehensive loss is comprised of the Company’s net loss and other comprehensive income (loss). Unrealized gain (loss) on available-for-sale marketable securities represents the only component of other comprehensive income (loss).
Clinical Trial Accruals	Clinical Trial Accruals The Company’s preclinical and clinical trials are performed by third party contract research organizations (CROs) and/or clinical investigators, and clinical supplies are manufactured by contract manufacturing organizations (CMOs). Invoicing from these third parties may be monthly based upon services performed or based upon milestones achieved. The Company accrues these expenses based upon its assessment of the status of each clinical trial and the work completed, and upon information obtained from the CROs and CMOs. The Company’s estimates are dependent upon the timeliness and accuracy of data provided by the CROs and CMOs regarding the status and cost of the studies, and may not match the actual services performed by the organizations. This could result in adjustments to the Company’s research and development expenses in future periods. To date the Company has had no significant adjustments.
Bonus Accruals	Bonus Accruals The Company has bonus programs for eligible employees. Bonuses are determined based on various criteria, including the achievement of corporate, departmental and individual goals. Bonus accruals are estimated based on various factors, including target bonus percentages per level of employee and probability of achieving the goals upon which bonuses are based. The Company’s management periodically reviews the progress made towards the goals under the bonus programs. As bonus accruals are dependent upon management’s judgments of the likelihood of achieving the various goals, it is possible for bonus expense to vary significantly in future periods if changes occur in those management estimates.
Segments	Segments The Company has one reportable segment and uses one measurement of results of operations to manage its business. All long-lived assets are maintained in the United States of America.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In November 2015, the Financial Accounting Standards Board (FASB) issued an accounting standard update for the presentation of deferred income taxes. Under this new guidance, deferred tax liabilities and assets should be classified as noncurrent in a classified balance sheet. The update is effective for the Company beginning in the first quarter of fiscal year 2017 with early adoption permitted as of the beginning of an interim or annual reporting period. Additionally, this guidance may be applied either prospectively or retrospectively to all periods presented. We adopted the standard in the first quarter of 2017 and it did not have a material impact to our consolidated financial statements. In May 2014, the 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. We will adopt the standard using the modified-retrospective approach beginning in 2018. We have completed our assessment of the impact and we do not expect a material impact to total revenue in our consolidated statement of operation and comprehensive loss. We do expect additional disclosures upon the adoption of the standard. In March 2016, the FASB issued an accounting standard update regarding Improvements to Employee – Share Based Payment Accounting that simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The Company adopted the standard effective January 1, 2017 and the adoption did not have a material effect on its consolidated financial statements. In February 2016, the FASB issued a new accounting standard that amends the guidance for the accounting and disclosure of leases. This new standard requires that lessees recognize the assets and liabilities that arise from leases on the balance sheet, including leases classified as operating leases under current GAAP, and disclose qualitative and quantitative information about leasing arrangements. The new standard requires a modified-retrospective approach to adoption and is effective for interim and annual periods beginning on January 1, 2019. The Company is in the process of evaluating the impact the adoption of this standard would have on its financial statements and disclosures. In May 2017, the FASB issued a new accounting standard update on stock compensation and the scope of modification accounting to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. Under this new guidance, modification accounting is required if the fair value, vesting conditions, or classification of the award changes as a result of the change in terms or conditions. The standard is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on its financial statements or disclosures.

Net Income (Loss) Per Common 25

Net Income (Loss) Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Reconciliation of Numerator and Denominator	The following is the calculation of basic and diluted net loss per share (in thousands, except share and per share data): Years Ended December 31, 2017 2016 Numerator: Net loss attributable to common shareholders $ (24,098 ) $ (12,600 ) Denominator: Weighted-average number of common shares outstanding - basic and diluted 11,400,881 213,420 Net loss per share: Basic and diluted $ (2.11 ) $ (59.04 )
Warrants and Options Split Adjusted, and Excluded from Computation of Diluted Net Income (Loss) Per Share	The following outstanding warrants and options were split adjusted, and excluded from the computation of diluted net loss per share for the periods presented because including them would have had an antidilutive effect (in thousands): Years Ended December 31, 2017 2016 Shares issuable upon exercise of warrants 3,332 35 Shares issuable upon exercise of stock options 2,769 942

Merger with Private Molecular (

Merger with Private Molecular (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Purchase Price for Threshold on Closing Date of Merger	The purchase price for Threshold on August 1, 2017, the closing date of the Merger, was as follows (in thousands, except per share amounts): August 1, 2017 Number of share of the combined company owned by Threshold stockholders 6,508 (1) Multiplied by the price per share of Threshold common stock $ 5.94 (2) Purchase price before options $ 38,658 Threshold options assumed 1,006 (3) Settlement of preexisting bridge note with Threshold (4,010 ) (4) Total purchase price $ 35,654 1. Represents the number of shares of common stock of the combined company that Threshold stockholders owned as of the closing of the Merger pursuant to the Merger Agreement. This amount is calculated as 6,508,356 shares from Threshold common stock outstanding as of August 1, 2017, adjusted for the 11-for-1 reverse stock split. 2. The fair value of Threshold common stock used in determining the purchase price was $5.94, which was derived from the $0.54 per share closing price of Threshold on August 1, 2017, the current price at the time of closing, adjusted for the 11-for-1 reverse stock split. 3. Because Private Molecular is considered to be the acquirer for accounting purposes, the pre-Merger vested stock options granted by Threshold under the 2014 Equity Incentive Plan are deemed to have been exchanged for equity awards of the Company and as such the portion of the acquisition date fair value of these equity awards attributable to pre-Merger service to Threshold were accounted for as a component of the consideration transferred. 4. Represent the bridge loan at the date of merger between Threshold and Molecular. Since the receivable on Threshold’s balance sheet was settled as part of the merger, it is deemed to be a reduction in the purchase price.
Summary of Allocation of Purchase Consideration to Assets Acquired and Liabilities Assumed	The following table summarizes the allocation of the purchase consideration to the assets acquired and liabilities assumed based on their fair values as of August 1, 2017 (in thousands): August 1, 2017 Cash and cash equivalents $ 11,216 Prepaid expenses and other current assets 945 In-process research and development (IPR&D) 26,623 Accounts payable, accrued expenses (2,009 ) Warrant liability (1,121 ) Net assets acquired $ 35,654
Pro Forma Results in Connection with Merger	The unaudited financial information in the following table summarizes the combined results of operations of the Company and Threshold, on a pro forma basis, as if the Merger occurred at the beginning of the periods presented (in thousands, except per share data). Unaudited Years ended December 31, 2017 2016 Revenue $ 6,395 $ 1,880 Net loss $ (15,599 ) $ (35,008 )

Marketable Securities and Fai27

Marketable Securities and Fair Value (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Financial Assets at Fair Value on Recurring Basis	The following table sets forth the Company’s financial assets (cash equivalents and available-for-sale marketable securities) at fair value on a recurring basis as of December 31, 2017 and 2016: Fair Value as December 31, Basis of Fair Value Measurements (in thousands) 2017 Level 1 Level 2 Level 3 Money market funds $ 51,751 $ 51,751 $ — $ — Fair Value as December 31, Basis of Fair Value Measurements (in thousands) 2016 Level 1 Level 2 Level 3 Money market funds $ 796 $ 796 $ — $ —
Summary of Company's Available-for-Sale Securities	The Company invests in highly-liquid, investment-grade securities. The following is a summary of the Company’s available-for-sale securities at December 31, 2017 and 2016: As of December 31, 2017 (in thousands): Cost Basis Unrealized Gain Unrealized Loss Fair Value Money market funds $ 51,751 $ — $ — $ 51,751 Less cash equivalents (51,751 ) — — (51,751 ) Total marketable securities $ — $ — $ — $ — As of December 31, 2016 (in thousands): Cost Basis Unrealized Gain Unrealized Loss Fair Value Money market funds $ 796 $ — $ — $ 796 Less cash equivalents (796 ) — — (796 ) Total marketable securities $ — $ — $ — $ —

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Components of Property and Equipment	Property and equipment comprise the following (in thousands): December 31, 2017 2016 Laboratory equipment $ 1,691 $ 488 Leasehold improvements 512 48 Furniture and fixtures 85 32 Computer and equipment 76 35 2,364 603 Less: Accumulated depreciation (412 ) (269 ) Total property and equipment, net $ 1,952 $ 334

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Components of Accrued Liabilities	Accrued liabilities comprise the following (in thousands): December 31, 2017 2016 Accrued liabilities: General and administrative $ 374 $ 26 Clinical costs 702 409 Non-clinical research 435 2 Bridge note interest — 201 Payroll related 1,149 553 Other accrued expenses 30 19 Total accrued liabilities $ 2,690 $ 1,210
Components of Deferred Revenue	Deferred revenue was comprised of the following: December 31, 2017 2016 Deferred revenue Grant agreements $ 1,673 $ 620 Collaboration agreements 1,092 1,250 Total deferred revenue $ 2,765 $ 1,870

Borrowing Arrangements (Tables)

Borrowing Arrangements (Tables)	12 Months Ended
	Dec. 31, 2017
Growth Capital Loan
Debt Instrument [Line Items]
Schedule of Required Future Principal Payments	Future required principal payments on the Growth Capital Loan were as follows as of December 31, 2017 (in thousands): Year Ending December 31, 2018 $ 2,400 2019 1,145 Total 3,545 Debt discount and deferred finance costs (67 ) Total $ 3,478

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Payments Due under Operating Lease Agreements	Future minimum payments due under the operating lease agreements at December 31, 2017 were as follows (in thousands): Year Ending December 31, 2018 $ 1,003 2019 1,135 2020 1,048 2021 1,074 2022 1,096 Thereafter 486 Total $ 5,842
Schedule of Future Minimum Capital Lease Payments	Future minimum capital lease payments consisted of the following at December 31, 2017 (in thousands): Year Ending December 31, 2018 $ 55 2019 33 2020 19 Total future minimum capital lease payments 107 Less amount representing interest (8 ) Total capital lease obligations 99 Current portion of lease obligations (50 ) Capital lease obligations, non-current portion $ 49

Redeemable Convertible Prefer32

Redeemable Convertible Preferred Stock (Tables)	12 Months Ended
	Dec. 31, 2017
Temporary Equity Disclosure [Abstract]
Summary of Redeemable Convertible Preferred Stock	The following is a summary of the Company’s redeemable convertible preferred stock at December 31, 2017 and 2016 (collectively, the “Preferred Stock”) (in thousands): Shares Issued and Outstanding Par Value Shares Authorized December 31, 2017 December 31, 2016 Series A Preferred Stock $ 0.001 2,500 — 2,500 Series B Preferred Stock $ 0.001 2,273 — 2,273 Series C Preferred Stock $ 0.001 4,392 — 4,343 Total 9,165 — 9,116
Schedule of Changes in the Preferred Stock	The following table presents changes in the preferred stock during the years ended December 31, 2017 and 2016 (in thousands): Series A Preferred Series B Preferred Series C Preferred Total Balance at December 31, 2015 $ 3,689 $ 5,174 $ 15,436 $ 24,299 Deemed dividends on preferred stock 200 306 1,066 1,572 Balance at December 31, 2016 $ 3,889 $ 5,480 $ 16,502 $ 25,871 Deemed dividends on preferred stock 119 178 661 958 Conversion to common stock in merger (4,008 ) (5,658 ) (17,163 ) (26,829 ) Balance at December 31, 2017 $ — $ — $ — $ —

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Reconciliation of Warrant Liability Measured at Fair Value	The following table is a reconciliation of the warrant liability measured at fair value using level 3 inputs (in thousands): Warrant Balance at December 31, 2015 34 Initial fair value of common stock warrants 18 Change in fair value of common stock warrants during 2016 (3 ) Balance at December 31, 2016 49 Change in fair value through August 1, 2017 37 Conversion of 2014 warrants to common stock (87 ) Warrant liability related to Merger on August 1, 2017 1,120 Change in fair value during the five months ended December 31, 2017 (165 ) Balance at December 31, 2017 $ 954
Outstanding Warrants Valuation Assumption	The fair value of these warrants on December 31, 2017 and 2016 was determined using a Black-Scholes model with the following key level 3 inputs: December 31, 2017 December 31, 2016 Risk-free interest rate 1.89 % 1.20 % Expected life (in years) 2.13 2.25 Dividend yield — — Volatility 103 % 76 % Stock price at valuation date $ 10.02 $ 3.07
Financial Liabilities Subject to Fair Value Measurements	The following table sets forth the Company’s financial liabilities subject to fair value measurements as of December 31, 2017 and 2016 (in thousands): Fair December 31, Basis of Fair Value Measurements (in thousands) 2017 Level 1 Level 2 Level 3 2017 warrants $ 954 $ — $ — $ 954 Fair December 31, Basis of Fair Value Measurements (in thousands) 2016 Level 1 Level 2 Level 3 2014 warrants $ 49 $ — $ — $ 49

Equity Incentive Plans and St34

Equity Incentive Plans and Stock Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity Under Equity Incentive Plan	The following table summarizes information about stock option activity assuming Threshold equity award plans were assumed by Private Molecular for years ended December 31, 2017 and 2016: Outstanding Weighted Weighted Aggregate Options Average Average Remaining Intrinsic Value Number of Exercise Contractual as of 12/31/2017 Shares Price Term (in millions) Balances, December 31, 2015 922,628 $ 0.89 6.6 $ 0.90 Options granted 31,845 1.85 Options exercised (1,513 ) 1.64 Options canceled (11,276 ) 1.10 Balances, December 31, 2016 941,684 $ 0.92 5.7 $ 0.90 Options assumed in merger (1) 963,681 33.62 Options granted 1,116,627 8.30 Options exercised (17,473 ) 3.66 Options canceled (235,808 ) 35.48 Balances, December 31, 2017 2,768,711 $ 12.07 5.6 $ 11.00 Vested and expected to vest December 31, 2017 2,768,711 $ 12.07 5.6 $ 11.00 Exercisable at December 31, 2017 1,634,268 $ 14.76 2.8 $ 8.90 (1) Private Molecular, as an accounting acquirer assumed stock options covering an aggregate of 963,681 shares of common stock.
Stock Options Outstanding and Exercisable by Exercise Price	At December 31, 2017, stock options outstanding and exercisable by exercise price were as follows: Options Outstanding Options Exercisable Range of Exercise Prices Number Outstanding Weighted Average Remaining Contractual Life (Years) Weighted Average Exercise Price Number Exercisable Weighted Average Exercise Price $ 0.42–0.71 480,949 2.14 $ 0.55 480,949 $ 0.55 $ 1.27–1.27 400,412 5.60 $ 1.27 393,560 $ 1.27 $ 1.85–6.05 328,929 4.76 $ 5.26 212,849 $ 5.60 $ 7.14–9.40 1,022,197 9.69 $ 8.64 10,686 $ 7.99 $ 14.30–42.57 277,168 1.53 $ 24.49 277,168 $ 24.49 $ 45.65–85.25 259,056 1.50 $ 59.00 259,056 $ 59.00 $ 0.42–85.25 2,768,711 5.62 $ 12.07 1,634,268 $ 14.76
Stock-Based Compensation Expense	Stock-based compensation expense, which consists of the compensation cost for employee stock options and the value of options issued to non-employees for services rendered, was allocated to research and development and general and administrative in the consolidated statements of operations as follows (in thousands): Years Ended December 31, 2017 2016 Stock-based compensation expense: Research and development $ 340 $ 0 General and administrative 1,452 109 $ 1,792 $ 109
Weighted-Average Fair Value Valuation Assumptions	The fair value of employee stock options was estimated using the following weighted-average assumptions for the years ended December 31, 2017 and 2016: Years Ended December 31, 2017 2016 Employee Stock Options Risk-free interest rate 2.06 % 1.25 % Expected life (in years) 6.07 5.00 Dividend yield — — Volatility 110 % 76 % Weighted-average fair value of stock options granted $ 6.94 $ 1.31

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Reconciliation of Income Taxes at Statutory Federal Income Tax Rate to Net Income Taxes	A reconciliation of income taxes at the statutory federal income tax rate to net income taxes included in the accompanying statements of operations is as follows (in thousands): 2017 2016 U.S. federal taxes (benefit) at statutory rate $ (7,867 ) $ (3,750 ) State federal income tax benefit (21 ) 10 Permanent differences 87 105 Research and development credits (237 ) (339 ) Change in valuation allowance due to operations 4,766 3,974 Acquisition-related permanent differences 2,281 — Expiring state carryovers and other 991 — Change in valuation allowance due to Tax Act (6,863 ) — U.S. Statutory Rate Change due to Tax Act 6,863 — Total $ — $ —
Schedule of Significant Components of Net Deferred Tax Assets	The tax effects of temporary differences that give rise to significant components of the net deferred tax assets are as follows (in thousands): December 31, 2017 2016 Deferred tax assets Net operating loss carryforward $ 13,797 $ 10,446 Research and development credits 5,060 $ 965 Deferred stock compensation 4,058 $ 8 Deferred revenue 581 636 Other 254 9 Total deferred tax assets 23,750 12,064 Total deferred tax liabilities Depreciable and amortizable assets (282 ) (329 ) R&D intangible assets (5,591 ) — Total deferred tax liabilities (5,873 ) (329 ) Less: Valuation allowance (17,877 ) (11,735 ) Net deferred tax assets $ — $ —
Schedule of Activity Related to Unrecognized Tax Benefits	The total amount of unrecognized benefits as of December 31, 2017 and 2016 was $1.1 million and $0, respectively. The reconciliation of unrecognized tax benefits at the beginning and end of the year is as follows: (in thousands) 2017 2016 Gross unrecognized tax benefits at January 1, $ — $ — Gross increases (decreases) related to acquisitions 1,064 — Gross increases (decreases) related to current year tax positions 79 — Gross unrecognized tax benefits at December 31, $ 1,143 $ —

Summary of Significant Accoun36

Summary of Significant Accounting Policies - Additional Information (Detail)	Aug. 01, 2017shares	Dec. 31, 2017USD ($)Segment	Dec. 31, 2016USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Reverse stock split of common stock, description		11-for-1 reverse stock split
Reverse stock split of common stock conversion ratio	11
Number of issued and outstanding shares of common stock converted into one issued and outstanding share of common stock	11
Number of issued and outstanding shares of common stock converted by every eleven shares of issued and outstanding common stock	1
Impairment of long lived assets | $		$ 0	$ 0
Reportable segment | Segment		1
Leasehold Improvements | Minimum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives		5 years
Leasehold Improvements | Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives		7 years
Takeda Pharmaceuticals Inc
Organization And Summary Of Significant Accounting Policies [Line Items]
Accounts receivable | $		$ 0	$ 0
Revenue | Credit Risk
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of total revenues		56.00%
Threshold
Organization And Summary Of Significant Accounting Policies [Line Items]
Reverse stock split of common stock, description	11-for-1 reverse stock split
Reverse stock split of common stock conversion ratio	11
Exchange ratio of company common stock shares exchanged for each share owned by private molecular stockholders	7.7844
Threshold equity holders ownership interest	34.40%
Private Molecular equity holders ownership interest	65.60%

Net Income (Loss) Per Common 37

Net Income (Loss) Per Common Share - Reconciliation of Numerator and Denominator (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net loss attributable to common shareholders	$ (24,098)	$ (12,600)
Denominator:
Weighted-average number of common shares outstanding - basic and diluted	11,400,881	213,420
Net loss per share:
Basic and diluted	$ (2.11)	$ (59.04)

Net Income (Loss) Per Common 38

Net Income (Loss) Per Common Share - Additional Information (Detail)	Aug. 01, 2017shares	Dec. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Reverse stock split of common stock conversion ratio	11
Reverse stock split of common stock, description		11-for-1 reverse stock split
Threshold
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Exchange ratio of company common stock shares exchanged for each share owned by private molecular stockholders	7.7844
Reverse stock split of common stock conversion ratio	11
Reverse stock split of common stock, description	11-for-1 reverse stock split

Net Income (Loss) Per Common 39

Net Income (Loss) Per Common Share - Warrants and Options Split Adjusted, and Excluded from Computation of Diluted Net Income (Loss) Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares issuable	3,332	35
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares issuable	2,769	942

Merger with Private Molecular -

Merger with Private Molecular - Additional Information (Detail)	Aug. 01, 2017USD ($)$ / sharesshares	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / shares	Jun. 01, 2017USD ($)	Mar. 24, 2017USD ($)
Business Acquisition [Line Items]
Reverse stock split of common stock, description				11-for-1 reverse stock split
Reverse stock split of common stock conversion ratio	11
Exercise price per share on stock options after reverse stock split | $ / shares				$ 8.30	$ 1.85
Stock compensation				$ 1,792,000	$ 109,000
Operating expenses				21,242,000	12,499,000
Loss on conversion of notes				4,619,000	0
2014 Equity Incentive Plan
Business Acquisition [Line Items]
Stock compensation				$ 1,200,000
Share Based Awards
Business Acquisition [Line Items]
Options to purchase shares of common stock | shares				963,681
Threshold
Business Acquisition [Line Items]
Reverse stock split of common stock, description	11-for-1 reverse stock split
Reverse stock split of common stock conversion ratio	11
Exchange ratio of company common stock shares exchanged for each share owned by private molecular stockholders | shares	7.7844
Threshold equity holders ownership interest	34.40%
Private Molecular equity holders ownership interest	65.60%
Threshold outstanding options assumed on merger date | shares	963,681
Exercise price per share on stock options after reverse stock split | $ / shares	$ 33.62
Stock compensation	$ 0
Settlement of threshold bridge loan	$ 4,010,000	$ 4,000,000
Fair value inputs discount rate	12.00%
Transaction costs associated with Merger	$ 2,000,000
Principal amount						$ 2,000,000	$ 2,000,000
Promissory note interest rate							1.00%
Operating expenses			$ 320,000
Threshold | Eliminations
Business Acquisition [Line Items]
Transaction costs associated with Merger			$ 5,400,000	$ 5,400,000	0
Loss on conversion of notes				4,600,000	0
Stock-based compensation expense				1,200,000	0
Severance costs				2,900,000	0
Interest expense				300,000	200,000
Interest expense				$ 100,000	$ 100,000
Threshold | In-process Research and Development (IPR&D)
Business Acquisition [Line Items]
Adjustment to previously recorded IPR&D due to correction of merger purchase price		$ 677,000

Merger with Private Molecular41

Merger with Private Molecular - Purchase Price for Threshold on Closing Date of Merger (Detail) - Threshold - USD ($) $ / shares in Units, $ in Thousands	Aug. 01, 2017	Sep. 30, 2017
Business Acquisition [Line Items]
Number of share of the combined company owned by Threshold stockholders	6,508,356
Multiplied by the price per share of Threshold common stock	$ 5.94
Purchase price before options	$ 38,658
Threshold options assumed	1,006
Settlement of preexisting bridge note with Threshold	(4,010)	$ (4,000)
Total purchase price	$ 35,654

Merger with Private Molecular42

Merger with Private Molecular - Purchase Price for Threshold on Closing Date of Merger (Parenthetical) (Detail)	Aug. 01, 2017$ / sharesshares	Dec. 31, 2017$ / shares	Dec. 31, 2016$ / shares
Business Acquisition [Line Items]
Reverse stock split of common stock, description		11-for-1 reverse stock split
Reverse stock split of common stock conversion ratio	11
Common stock closing price		$ 10.02	$ 3.07
Threshold
Business Acquisition [Line Items]
Number of share of the combined company owned by Threshold stockholders | shares	6,508,356
Reverse stock split of common stock, description	11-for-1 reverse stock split
Reverse stock split of common stock conversion ratio	11
Price per share of Threshold common stock	$ 5.94
Common stock closing price	$ 0.54

Merger with Private Molecular43

Merger with Private Molecular - Summary of Allocation of Purchase Consideration to Assets Acquired and Liabilities Assumed (Detail) - Threshold $ in Thousands	Aug. 01, 2017USD ($)
Business Acquisition [Line Items]
Cash and cash equivalents	$ 11,216
Prepaid expenses and other current assets	945
In-process research and development (IPR&D)	26,623
Accounts payable, accrued expenses	(2,009)
Warrant liability	(1,121)
Net assets acquired	$ 35,654

Merger with Private Molecular44

Merger with Private Molecular - Pro Forma Results in Connection with Merger (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Business Combinations [Abstract]
Revenue	$ 6,395	$ 1,880
Net loss	$ (15,599)	$ (35,008)

Research and Development Agreem

Research and Development Agreements - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended		74 Months Ended
	Nov. 30, 2011	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Oct. 31, 2016
Research And Development Collaboration Agreements [Line Items]
Collaboration revenue				$ 2,408,000	$ 0
Grant revenue				987,000	1,880,000
Other Collaboration Agreements | ETBs
Research And Development Collaboration Agreements [Line Items]
Collaboration revenue			$ 500,000
Collaboration revenue receivable				250,000		$ 250,000
Takeda Pharmaceuticals Inc | Takeda Collaboration Agreement
Research And Development Collaboration Agreements [Line Items]
Upfront payment for technology access fees and cost reimbursement							$ 2,000,000
Collaboration revenue				1,900,000
Takeda Pharmaceuticals Inc | Takeda Multi Target Agreement
Research And Development Collaboration Agreements [Line Items]
Collaboration revenue				0
Upfront technology access fee				1,000,000
Additional fee received upon designation of each of two targets				2,000,000		2,000,000
Aggregate milestones receivable upon exercise of option to license ETBS				25,000,000		25,000,000
Clinical development and commercialization milestone entitled to potentially receive				547,000,000		547,000,000
Aggregate purchase price		$ 20,000,000
Cancer Prevention and Research Institute of Texas | Grant Agreements | ETB MT-3724
Research And Development Collaboration Agreements [Line Items]
Product development grant awarded	$ 10,600,000
Cancer Prevention and Research Institute of Texas | Grant Agreements | Product Development Grant | ETB MT-3724
Research And Development Collaboration Agreements [Line Items]
Grant revenue				$ 1,000,000	$ 1,900,000	$ 9,500,000

Marketable Securities and Fai46

Marketable Securities and Fair Value - Financial Assets at Fair Value on Recurring Basis (Detail) - Money Market Funds - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$ 51,751	$ 796
Basis of Fair Value Measurements, Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	51,751	796
Basis of Fair Value Measurements, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Basis of Fair Value Measurements, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$ 0	$ 0

Marketable Securities and Fai47

Marketable Securities and Fair Value - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Aug. 01, 2017	Dec. 31, 2015	Dec. 31, 2014
Investments Debt And Equity Securities [Abstract]
Shares of common stock to be purchased with warrants	377,273	17,310	377,273	17,310	14,254
Realized gain or losses	$ 0	$ 0
Long-term debt, carrying value	$ 3,500,000	$ 5,600,000

Marketable Securities and Fai48

Marketable Securities and Fair Value - Summary of Company's Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	$ 0	$ 0
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	0	0
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	51,751	796
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	51,751	796
Less Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	51,751	796
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	$ 51,751	$ 796

Property and Equipment - Compon

Property and Equipment - Components of Property and Equipment (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Total property and equipment, Gross	$ 2,364,000	$ 603,000
Less: Accumulated depreciation	(412,000)	(269,000)
Total property and equipment, net	1,952,000	334,000
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property and equipment, Gross	1,691,000	488,000
Less: Accumulated depreciation	(75,000)	(44,000)
Total property and equipment, net	162,000	136,000
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment, Gross	512,000	48,000
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment, Gross	85,000	32,000
Computer and Equipment
Property Plant And Equipment [Line Items]
Total property and equipment, Gross	$ 76,000	$ 35,000

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Depreciation	$ 155,000	$ 65,000

Balance Sheet Components - Comp

Balance Sheet Components - Components of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued Liabilities Current [Abstract]
General and administrative	$ 374	$ 26
Clinical costs	702	409
Non-clinical research	435	2
Bridge note interest	0	201
Payroll related	1,149	553
Other accrued expenses	30	19
Total accrued liabilities	$ 2,690	$ 1,210

Balance Sheet Components - Co52

Balance Sheet Components - Components of Deferred Revenue (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 2,765	$ 1,870
Grant Agreements
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	1,673	620
Collaboration Agreements
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 1,092	$ 1,250

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($)	Aug. 01, 2017	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Bridge note interest		$ 0	$ 201,000
Loss on conversion of notes		$ 4,619,000	0
Threshold Pharmaceuticals, Inc. Promissory Note
Related Party Transaction [Line Items]
Aggregate proceeds received from promissory note payable to Threshold Pharmaceuticals, Inc	$ 4,000,000
Longitude Venture Partners III, L..P. | Concurrent Financing
Related Party Transaction [Line Items]
Ownership percentage of merger company		15.30%
Investments		$ 20,000,000
CDK Associates, L.L.C. | Concurrent Financing
Related Party Transaction [Line Items]
Ownership percentage of merger company		5.55%
Investments		$ 7,000,000
Excel Venture Fund II, L.P. | Concurrent Financing
Related Party Transaction [Line Items]
Investments		$ 333,000
Excel Venture Fund II, L.P. | Concurrent Financing | Minimum
Related Party Transaction [Line Items]
Ownership percentage of merger company		5.00%
Secured Convertible Promissory Notes
Related Party Transaction [Line Items]
Proceeds from stockholders	$ 10,000,000		$ 7,300,000
Interest accrual rate		5.00%
Debt instrument maturity date		Sep. 7, 2017
Convertible notes price per share		$ 3.36
Debt principal amount		$ 10,000,000
Bridge note interest		$ 486,900
Number of shares issued upon debt conversion		3,121,098
Loss on conversion of notes		$ 4,600,000
Secured Convertible Promissory Notes | Common Stock | Threshold
Related Party Transaction [Line Items]
Number of post split shares issued in merger		2,208,716

Borrowing Arrangements - Additi

Borrowing Arrangements - Additional Information - (Detail)	1 Months Ended			12 Months Ended
	Apr. 30, 2016USD ($)$ / sharesshares	Jun. 30, 2015USD ($)$ / sharesshares	May 31, 2015USD ($)	Dec. 31, 2017USD ($)Installment	Dec. 31, 2016USD ($)$ / shares	Aug. 01, 2017$ / shares	Dec. 31, 2015$ / shares	Apr. 30, 2015USD ($)shares	Dec. 31, 2014$ / shares
Debt Instrument [Line Items]
Common stock exercise price | $ / shares					$ 3.07	$ 39.82	$ 3.07		$ 3.07
Growth Capital Loan
Debt Instrument [Line Items]
Debt instrument principal paid during period				$ 2,400,000	$ 237,000
Debt instrument interest paid during period				$ 400,000	220,000
Debt Instrument, covenant description				The Company does not have any financial loan covenants related to the Growth Capital Loan.
Total debt				$ 3,545,000	$ 5,600,000
SVB
Debt Instrument [Line Items]
Debt instrument, frequency of periodic payment				3
Maximum borrowing capacity under loan								$ 6,000,000
Number of warrants to purchase shares of common stock | shares	17,310	17,310						14,254
Final fee due at loan maturity date								$ 345,000
Amount drew down from bank	$ 3,000,000	$ 2,300,000	$ 800,000
Common stock exercise price | $ / shares	$ 3.07	$ 3.07
SVB | Loan and Security Agreement
Debt Instrument [Line Items]
Debt instrument, frequency of periodic payment				30
Amount drew down from bank				$ 6,000,000
Debt instrument first installment due date				Nov. 1, 2016
Debt instrument maturity date				Apr. 30, 2019
Interest accrual rate				5.44%
Number of frequency of consecutive equal monthly payments of principal plus interest paid | Installment				30
SVB | Loan and Security Agreement | Prime Rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				1.19%

Borrowing Arrangements - Schedu

Borrowing Arrangements - Schedule of Required Future Principal Payments - (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total	$ 3,500	$ 5,600
Growth Capital Loan
Debt Instrument [Line Items]
2,018	2,400
2,019	1,145
Total	3,545	$ 5,600
Debt discount and deferred finance costs	(67)
Total	$ 3,478

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Other Commitments [Line Items]
Property and equipment, net	$ 1,952,000	$ 334,000
Accumulated amortization	412,000	269,000
Facilities
Other Commitments [Line Items]
Operating lease expense	625,000,000	288,000,000
Laboratory Equipment
Other Commitments [Line Items]
Property and equipment, net	162,000	136,000
Accumulated amortization	$ 75,000	$ 44,000

Commitments and Contingencies57

Commitments and Contingencies - Future Minimum Payments Due under Operating Lease Agreements (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Leases [Abstract]
2,018	$ 1,003
2,019	1,135
2,020	1,048
2,021	1,074
2,022	1,096
Thereafter	486
Total	$ 5,842

Commitments and Contingencies58

Commitments and Contingencies - Schedule of Future Minimum Capital Lease Payments (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,018	$ 55
2,019	33
2,020	19
Total future minimum capital lease payments	107
Less amount representing interest	(8)
Total capital lease obligations	99
Current portion of lease obligations	(50)
Capital lease obligations, non-current portion	$ 49

Redeemable Convertible Prefer59

Redeemable Convertible Preferred Stock - Summary of Redeemable Convertible Preferred Stock (Detail) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized		9,165
Redeemable convertible preferred stock, shares issued and outstanding	0	9,116
Series A Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, par value		$ 0.001
Redeemable convertible preferred stock, shares authorized		2,500
Redeemable convertible preferred stock, shares issued and outstanding	0	2,500
Series B Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, par value		$ 0.001
Redeemable convertible preferred stock, shares authorized		2,273
Redeemable convertible preferred stock, shares issued and outstanding	0	2,273
Series C Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, par value		$ 0.001
Redeemable convertible preferred stock, shares authorized		4,392
Redeemable convertible preferred stock, shares issued and outstanding	0	4,343

Redeemable Convertible Prefer60

Redeemable Convertible Preferred Stock - Additional Information (Detail) - shares	Aug. 01, 2017	Dec. 31, 2017
Common Stock
Temporary Equity [Line Items]
Preferred stock converted into common stock in connection with merger, shares	13,029,297
Conversion of preferred stock to common stock in connection with merger, shares	9,220,478	9,220,478
Convertible Preferred Stock
Temporary Equity [Line Items]
Temporary equity, Amount of shares of preferred stock outstanding that were converted to common stock in connection with merger	9,116,405	9,116,405
Conversion of preferred stock dividends to common stock in connection with merger, shares	3,912,892

Redeemable Convertible Prefer61

Redeemable Convertible Preferred Stock - Schedule of Changes in the Preferred Stock (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Temporary Equity [Line Items]
Beginning balance	$ 25,871	$ 24,299
Deemed dividends on preferred stock	958	1,572
Conversion Of Preferred Stock In To Common Stock Upon Merger	(26,829)
Ending balance	0	25,871
Series A Preferred
Temporary Equity [Line Items]
Beginning balance	3,889	3,689
Deemed dividends on preferred stock	119	200
Conversion Of Preferred Stock In To Common Stock Upon Merger	(4,008)
Ending balance	0	3,889
Series B Preferred
Temporary Equity [Line Items]
Beginning balance	5,480	5,174
Deemed dividends on preferred stock	178	306
Conversion Of Preferred Stock In To Common Stock Upon Merger	(5,658)
Ending balance	0	5,480
Series C Preferred
Temporary Equity [Line Items]
Beginning balance	16,502	15,436
Deemed dividends on preferred stock	661	1,066
Conversion Of Preferred Stock In To Common Stock Upon Merger	(17,163)
Ending balance	$ 0	$ 16,502

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	Aug. 01, 2017	Jun. 23, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class Of Warrant Or Right [Line Items]
Warrant exercise price	$ 39.82				$ 3.07	$ 3.07	$ 3.07
Warrants to purchase shares of common stock	377,273		377,273	377,273	17,310	17,310	14,254
Common Stock | 2017 Warrants
Class Of Warrant Or Right [Line Items]
Warrant exercise price			$ 39.82	$ 39.82
Warrants to purchase shares of common stock			377,273	377,273
Preferred Stock | 2014 Warrants
Class Of Warrant Or Right [Line Items]
Warrant exercise price					$ 3.07
Warrants to purchase shares of common stock					48,874
Concurrent Financing
Class Of Warrant Or Right [Line Items]
Aggregate purchase price		$ 20,000,000
Each unit of shares transaction of common stock		2,922,993
Purchase price per share		$ 6.8423
Warrants
Class Of Warrant Or Right [Line Items]
Change in fair value of common stock warrants				$ 128,000
Wedbush Agreement | PIPE Financing | Common Stock
Class Of Warrant Or Right [Line Items]
Warrant exercisable period			7 years
Warrant exercise price			$ 6.8423	$ 6.8423
Warrants to purchase shares of common stock			57,930	57,930
Private Placement | Longitude Venture Partners III, L..P. | PIPE Financing
Class Of Warrant Or Right [Line Items]
Number of aggregate units sold	5,793,063
Aggregate purchase price	$ 40,000,000
Each unit of shares transaction of common stock	1
Warrants to purchase shares of common stock	0.5
Sale of units, description and its composition				the Company sold an aggregate of 5,793,063 units (the “Units”) having an aggregate purchase price of $40.0 million (“PIPE Financing”), each such Unit consisting of (i) one (1) share (the “Shares”) of our common stock and (ii) a warrant (the “Warrants”) to purchase 0.5 shares of our common stock (the “Private Placement”).
Purchase price per unit	$ 6.9048
Warrant exercisable period	7 years
Warrant exercise price	$ 6.8423
Warrants to purchase shares of common stock			2,896,532	2,896,532

Stockholders' Equity - Reconcil

Stockholders' Equity - Reconciliation of Warrant Liability Measured at Fair Value (Detail) - USD ($) $ in Thousands	Aug. 01, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Change in common stock warrant fair value			$ 128	$ 3
Basis of Fair Value Measurements, Level 3
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance			49	34
Fair value of common stock warrants			1,120	18
Change in common stock warrant fair value	$ 37	$ (165)		(3)
Ending Balance		$ 954	954	$ 49
Conversion of 2014 warrants to common stock			$ (87)

Stockholders' Equity - Outstand

Stockholders' Equity - Outstanding Warrants Valuation Assumption (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Risk-free interest rate	1.89%	1.20%
Expected life (in years)	2 years 1 month 17 days	2 years 3 months
Dividend yield	0.00%	0.00%
Volatility	103.00%	76.00%
Stock price at valuation date	$ 10.02	$ 3.07

Stockholders' Equity - Financia

Stockholders' Equity - Financial Liabilities Subject to Fair Value Measurements (Detail) - Warrants - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
2017 Warrants
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements	$ 954
2017 Warrants | Basis of Fair Value Measurements, Level 1
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements	0
2017 Warrants | Basis of Fair Value Measurements, Level 2
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements	0
2017 Warrants | Basis of Fair Value Measurements, Level 3
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements	$ 954
2014 Warrants
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements		$ 49
2014 Warrants | Basis of Fair Value Measurements, Level 1
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements		0
2014 Warrants | Basis of Fair Value Measurements, Level 2
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements		0
2014 Warrants | Basis of Fair Value Measurements, Level 3
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Financial liabilities subject to fair value measurements		$ 49

Equity Incentive Plans and St66

Equity Incentive Plans and Stock Based Compensation - Additional Information (Detail) - USD ($)	Jan. 01, 2017	Jan. 01, 2016	Aug. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total intrinsic value of stock options exercised				$ 78,000	$ 0
Cash received from stock option exercises				61,000	2,000
Tax benefit realized upon exercise of option				0
Stock-based compensation expense				1,792,000	$ 109,000
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans				$ 7,100,000
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans, period for recognition				3 years 6 months
2009 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares of common stock issuable under plan				1,452,268
Terms of stock options vested				5 years
Percentage of shares vesting on one-year anniversary and equal monthly vesting installments thereafter				20.00%
Options to purchase shares of common stock available for future grants				101,667
2014 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Terms of stock options vested				4 years
Options to purchase shares of common stock available for future grants				637,029
Percentage of fair market value			100.00%
Terms of stock options granted				10 years
Stock-based compensation expense				$ 1,200,000
2004 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Terms of stock options vested				4 years
Percentage of fair market value				100.00%
Terms of stock options granted				10 years
2004 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options to purchase shares of common stock available for future grants				18,917
Additional shares authorized for issuance	9,091	9,091
Offering period				24 months
Purchase period				6 months
Discount available to eligible employees related to employee stock purchase plan				85.00%
Plan participants purchased shares				2,868	8,368
Average purchase price under 2004 Employee Stock Purchase Plan				$ 2.80	$ 2.75

Equity Incentive Plans and St67

Equity Incentive Plans and Stock Based Compensation - Summary of Stock Option Activity Under Equity Incentive Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding Options Number of Shares, Beginning Balance	941,684	922,628
Number of Shares, Options assumed in merger	963,681
Number of Shares, Options granted	1,116,627	31,845
Number of Shares, Options exercised	(17,473)	(1,513)
Number of shares, Options canceled	(235,808)	(11,276)
Outstanding Options Number of Shares, Ending Balance	2,768,711	941,684	922,628
Outstanding Options Number of Shares, Vested and expected to vest	2,768,711
Outstanding Options Number of Shares, Exercisable	1,634,268
Weighted Average Exercise Price, Beginning Balance	$ 0.92	$ 0.89
Weighted Average Exercise Price, Options assumed in merger	33.62
Weighted Average Exercise Price, Options granted	8.30	1.85
Weighted Average Exercise Price, Options exercised	3.66	1.64
Weighted Average Exercise Price, Options canceled	35.48	1.10
Weighted Average Exercise Price, Ending Balance	12.07	$ 0.92	$ 0.89
Weighted Average Exercise Price, Vested and expected to vest	12.07
Weighted Average Exercise Price, Exercisable	$ 14.76
Weighted-Average Remaining Contractual Term, Outstanding	5 years 7 months 6 days	5 years 8 months 12 days	6 years 7 months 6 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	5 years 7 months 6 days
Weighted-Average Remaining Contractual Term, Exercisable	2 years 9 months 18 days
Aggregate Intrinsic Value, Outstanding	$ 900	$ 900
Aggregate Intrinsic Value, Outstanding	11,000	$ 900	$ 900
Aggregate Intrinsic Value, Vested and expected to vest	11,000
Aggregate Intrinsic Value, Exercisable	$ 8,900

Equity Incentive Plans and St68

Equity Incentive Plans and Stock Based Compensation - Summary of Stock Option Activity Under Equity Incentive Plan (Parenthetical) (Detail)	Aug. 01, 2017shares
Private Molecular
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Threshold Pharmaceuticals, Inc. options assumed in merger with Molecular Templates, Inc.	963,681

Equity Incentive Plans and St69

Equity Incentive Plans and Stock Based Compensation - Stock Options Outstanding and Exercisable by Exercise Price (Detail)	12 Months Ended
	Dec. 31, 2017$ / sharesshares
$ 0.42–0.71
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices	$ 0.42
Range of Exercise Prices	$ 0.71
Number Outstanding | shares	480,949
Weighted Average Remaining Contractual Life (Years)	2 years 1 month 20 days
Weighted Average Exercise Price	$ 0.55
Number Exercisable | shares	480,949
Weighted Average Exercise Price	$ 0.55
$ 1.27–1.27
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices	1.27
Range of Exercise Prices	$ 1.27
Number Outstanding | shares	400,412
Weighted Average Remaining Contractual Life (Years)	5 years 7 months 6 days
Weighted Average Exercise Price	$ 1.27
Number Exercisable | shares	393,560
Weighted Average Exercise Price	$ 1.27
$ 1.85–6.05
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices	1.85
Range of Exercise Prices	$ 6.05
Number Outstanding | shares	328,929
Weighted Average Remaining Contractual Life (Years)	4 years 9 months 3 days
Weighted Average Exercise Price	$ 5.26
Number Exercisable | shares	212,849
Weighted Average Exercise Price	$ 5.60
$ 7.14–9.40
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices	7.14
Range of Exercise Prices	$ 9.40
Number Outstanding | shares	1,022,197
Weighted Average Remaining Contractual Life (Years)	9 years 8 months 8 days
Weighted Average Exercise Price	$ 8.64
Number Exercisable | shares	10,686
Weighted Average Exercise Price	$ 7.99
$ 14.30–42.57
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices	14.30
Range of Exercise Prices	$ 42.57
Number Outstanding | shares	277,168
Weighted Average Remaining Contractual Life (Years)	1 year 6 months 10 days
Weighted Average Exercise Price	$ 24.49
Number Exercisable | shares	277,168
Weighted Average Exercise Price	$ 24.49
$ 45.65–85.25
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices	45.65
Range of Exercise Prices	$ 85.25
Number Outstanding | shares	259,056
Weighted Average Remaining Contractual Life (Years)	1 year 6 months
Weighted Average Exercise Price	$ 59
Number Exercisable | shares	259,056
Weighted Average Exercise Price	$ 59
$ 0.42–85.25
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices	0.42
Range of Exercise Prices	$ 85.25
Number Outstanding | shares	2,768,711
Weighted Average Remaining Contractual Life (Years)	5 years 7 months 13 days
Weighted Average Exercise Price	$ 12.07
Number Exercisable | shares	1,634,268
Weighted Average Exercise Price	$ 14.76

Equity Incentive Plans and St70

Equity Incentive Plans and Stock Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,792	$ 109
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	340	0
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,452	$ 109

Equity Incentive Plans and St71

Equity Incentive Plans and Stock Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail) - Employee Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	2.06%	1.25%
Expected life (in years)	6 years 25 days	5 years
Dividend yield	0.00%	0.00%
Volatility	110.00%	76.00%
Weighted-average fair value of stock options granted	$ 6.94	$ 1.31

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes Disclosure [Line Items]
U.S. corporate income tax rate		35.00%
Valuation allowance recorded to offset income tax expense from revaluation of deferred tax assets and liabilities due to corporate tax rate change		$ 6,863,000	$ 0
Income tax expense from revaluation of deferred tax assets and liabilities due to change corporate tax rate		$ 6,900,000
Description of foreign operations		The Company currently has one foreign subsidiary that has not commenced operations.
Increase in valuation allowance				$ 4,800,000
Unrecognized benefits		$ 1,143,000	0	$ 0
Accrued interest or penalties		0	$ 0
Unrecognized tax benefits expected to be recognized in next twelve months		79,000
Federal
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards		$ 63,200,000
Year net operating loss carryforwards begin to expire		2,021
Research and development credits		$ 1,100,000
Year research and development credits begin to expire		2,022
State
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards		$ 7,600,000
Year net operating loss carryforwards begin to expire		2,017
Research and development credits		$ 4,900,000
Scenario, Plan
Income Taxes Disclosure [Line Items]
U.S. corporate income tax rate	21.00%

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Income Taxes at Statutory Federal Income Tax Rate to Net Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
U.S. federal taxes (benefit) at statutory rate	$ (7,867)	$ (3,750)
State federal income tax benefit	(21)	10
Permanent differences	87	105
Research and development credits	(237)	(339)
Change in valuation allowance due to operations	4,766	3,974
Acquisition-related permanent differences	2,281	0
Expiring state carryovers and other	991	0
Change in valuation allowance due to Tax Act	(6,863)	0
U.S. Statutory Rate Change due to Tax Act	6,863	0
Total	$ 0	$ 0

Income Taxes - Schedule of Sign

Income Taxes - Schedule of Significant Components of Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets
Net operating loss carryforward	$ 13,797	$ 10,446
Research and development credits	5,060	965
Deferred stock compensation	4,058	8
Deferred revenue	581	636
Other	254	9
Total deferred tax assets	23,750	12,064
Total deferred tax liabilities
Depreciable and amortizable assets	(282)	(329)
R&D intangible assets	(5,591)	0
Total deferred tax liabilities	(5,873)	(329)
Less: Valuation allowance	(17,877)	(11,735)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Schedule of Acti

Income Taxes - Schedule of Activity Related to Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits at January 1,	$ 0	$ 0
Gross increases (decreases) related to acquisitions	1,064	0
Gross increases (decreases) related to current year tax positions	79	0
Gross unrecognized tax benefits at December 31,	$ 1,143	$ 0

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Molecular Templates 401(k) Plan
Defined Contribution Plan Disclosure [Line Items]
Vesting period for Company's matching contribution	3 years
Percentage of Company's matching contribution vested after year one	25.00%
Percentage of Company's matching contribution vested after year two	50.00%
Percentage of Company's matching contribution vested after year three	100.00%
Employer discretionary contribution amount	$ 0	$ 43,000
Threshold Pharmaceuticals 401(k) Plan
Defined Contribution Plan Disclosure [Line Items]
Employer discretionary contribution amount	$ 0

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($)	Feb. 27, 2018	Aug. 01, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Subsequent Event [Line Items]
Warrant exercise price		$ 39.82	$ 3.07	$ 3.07	$ 3.07
Subsequent Event | Term Loan Facility | Perceptive
Subsequent Event [Line Items]
Maximum borrowing capacity under Credit Facility	$ 10,000,000
Increase in applicable margin percentage on event of default	4.00%
Credit Facility, quarterly amortization amount after second anniversary of closing date	$ 200,000
Credit Facility, maturity date	Feb. 27, 2022
Exit fee	$ 100,000
Subsequent Event | Term Loan Facility | Perceptive | Common Stock
Subsequent Event [Line Items]
Number of shares issued for each warrant	190,000
Warrant exercisable period	7 years
Warrant exercise price	$ 9.5792
Subsequent Event | Term Loan Facility | Perceptive | LIBOR
Subsequent Event [Line Items]
Debt instrument, basis spread on variable rate	11.00%
Subsequent Event | Term Loan Facility | Perceptive | Term Loan Drawn on Effective Date of Credit Facility
Subsequent Event [Line Items]
Proceeds from initial term loan on closing date of Credit Facility	$ 5,000,000
Subsequent Event | Term Loan Facility | Perceptive | Additional Term Loan Drawn Six Months Following Effective Date of Credit Facility
Subsequent Event [Line Items]
Maximum borrowing capacity under Credit Facility	$ 5,000,000