Endocyte (ECYT) 10-Q 9 May 18 2018 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Entity Registrant Name	ENDOCYTE INC
Entity Central Index Key	1,235,007
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		69,501,640

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents at carrying value	$ 89,831,744	$ 18,559,130
Short-term investments	83,292,883	78,912,297
Receivables		273,044
Prepaid expenses	1,259,420	751,255
Other assets	172,390	77,077
Total current assets	174,556,437	98,572,803
Property and equipment, net	1,942,852	2,182,399
Other noncurrent assets	178,941	7,067
Total assets	176,678,230	100,762,269
Current liabilities:
Accounts payable	1,414,607	376,394
Accrued wages and benefits	1,120,772	2,533,133
Accrued clinical trial expenses	1,007,396	689,985
Accrued expenses and other liabilities	1,070,302	946,668
Total current liabilities	4,613,077	4,546,180
Deferred revenue, net of current portion	363,266	731,944
Total liabilities	4,976,343	5,278,124
Stockholders’ equity:
Common stock: $0.001 par value, 100,000,000 shares authorized; 48,203,529 and 69,427,773 shares issued and outstanding at December 31, 2017 and March 31, 2018	69,428	48,204
Additional paid-in capital	488,929,377	404,454,909
Accumulated other comprehensive (loss) income	(79,143)	(64,433)
Retained deficit	(317,217,775)	(308,954,535)
Total stockholders’ equity	171,701,887	95,484,145
Total liabilities and stockholders’ equity	$ 176,678,230	$ 100,762,269

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	69,427,773	48,203,529
Common stock, shares outstanding	69,427,773	48,203,529

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue:
Collaboration revenue	$ 15,855	$ 12,500
Total revenue	15,855	12,500
Operating expenses:
Research and development	5,255,065	7,994,472
General and administrative	3,777,546	3,745,262
Total operating expenses	9,032,611	11,739,734
Loss from operations	(9,016,756)	(11,727,234)
Other income (expense), net:
Interest income, net	412,897	235,451
Other income (expense), net	1,213	3,198
Net loss	$ (8,602,646)	$ (11,488,585)
Net loss per share -basic and diluted (in dollars per share)	$ (0.16)	$ (0.27)
Items included in other comprehensive income (loss):
Unrealized gain (loss) and amounts reclassified to net loss on available-for-sale securities	$ (14,710)	$ (12,681)
Other comprehensive income (loss)	(14,710)	(12,681)
Comprehensive loss	$ (8,617,356)	$ (11,501,266)
Weighted-average number of common shares used in net loss per share calculation - basic and diluted (in shares)	55,000,743	42,434,709

CONDENSED STATEMENT OF STOCKHOL

CONDENSED STATEMENT OF STOCKHOLDERS' EQUITY (DEFICIT) - USD ($)	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Deficit	Total
Balance at beginning of period at Dec. 31, 2016			$ (41,196)
Net loss					$ (11,488,585)
Unrealized gain (loss) on securities					(12,681)
Balance at end of period at Mar. 31, 2017			(53,877)
Cumulative Effect of New Accounting Principle in Period of Adoption | ASU 2014-09				$ 339,406	339,406
Balance after adjustment	$ 48,204	$ 404,454,909	(64,433)	(308,615,129)	95,823,551
Balance at beginning of period at Dec. 31, 2017	$ 48,204	404,454,909	(64,433)	(308,954,535)	95,484,145
Balances (in shares) at Dec. 31, 2017	48,203,529
Exercise of stock options	$ 561	2,302,412			$ 2,302,973
Exercise of stock options (in shares)	561,088				561,088
Stock-based compensation	$ 127	1,251,211			$ 1,251,338
Stock-based compensation (in shares)	127,442
Issuance of common stock in connection with equity offering	$ 20,536	80,920,845			80,941,381
Issuance of common stock in connection with equity offering (in shares)	20,535,714
Net loss				(8,602,646)	(8,602,646)
Unrealized gain (loss) on securities			(14,710)		(14,710)
Balance at end of period at Mar. 31, 2018	$ 69,428	$ 488,929,377	$ (79,143)	$ (317,217,775)	$ 171,701,887
Balances (in shares) at Mar. 31, 2018	69,427,773

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net income (loss)	$ (8,602,646)	$ (11,488,585)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	202,644	238,347
Stock-based compensation	1,355,800	1,132,519
Loss on disposal of property and equipment	(1,213)	2,222
Amortization of Debt Discount (Premium)	(192,298)
Accretion of bond premium		43,001
Change in operating assets and liabilities:
Receivables	177,731	22,435
Prepaid expenses and other assets	(337,374)	396,962
Accounts payable	863,915	(3,085)
Accrued wages, benefits and other liabilities	(1,155,713)	(814,721)
Deferred revenue	(15,855)	(12,500)
Net cash used in operating activities	(7,705,009)	(10,483,405)
Investing activities
Purchases of property and equipment	(5,225)	(29,536)
Proceeds from disposal of property and equipment	46,580
Purchases of investments	27,703,624	14,977,694
Proceeds from sale and maturities of investments	23,500,000	28,000,000
Net cash provided by investing activities	(4,162,269)	12,992,770
Financing activities
Stock repurchase	(104,462)	(92,929)
Proceeds from issuance of common stock in connection with equity offering	80,941,381
Proceeds from the exercise of stock options	2,302,973	16,290
Net cash provided by financing activities	83,139,892	(76,639)
Net increase (decrease) in cash and cash equivalents	71,272,614	2,432,726
Cash and cash equivalents at beginning of period	18,559,130	31,228,192
Cash and cash equivalents at end of period	$ 89,831,744	$ 33,660,918

Nature of Business and Organiza

Nature of Business and Organization	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business and Organization	1. Nature of Business and Organization Endocyte, Inc. (the “Company”) is a biopharmaceutical company and leader in developing targeted therapies for the treatment of cancer. The Company uses drug conjugation technology to create novel therapeutics and companion imaging agents for personalized targeted therapies. The agents actively target receptors that are over-expressed on diseased cells relative to healthy cells, such as prostate specific membrane antigen (“PSMA”) in prostate cancer. This targeted approach is designed to safely enable the delivery of highly potent drug payloads. The companion imaging agents are designed to identify patients whose disease over-expresses the target of the therapy and who are therefore more likely to benefit from treatment . In September 2017, the Company entered into a Development and License Agreement (the “License Agreement”) with ABX advanced biochemical compounds – Biomedizinische Forschungsreagenzien GmbH (“ABX”), pursuant to which the Company acquired exclusive worldwide rights to develop and commercialize PSMA-617 agents, including the product candidate known as 177 Lu-PSMA-617, a radioligand therapeutic (“RLT”). Following a successful End of Phase 2 meeting with the U.S. Food and Drug Administration (“FDA”), the Company finalized the phase 3 VISION trial design and registration plan for 177 Lu-PSMA-617. The trial will include two interim assessments of efficacy, which could potentially lead to an early approval for 177 Lu-PSMA-617. The Company intends to initiate, in the second quarter of 2018, the VISION trial, an international, prospective, open-label, multicenter, randomized phase 3 study of 177 Lu-PSMA-617 in up to 750 patients with progressive PSMA-positive metastatic castration-resistant prostate cancer (“mCRPC”) who have received at least one novel androgen axis drug (“NAAD”) and at least one taxane regimen. On October 2, 2017, the Company announced its plan to primarily focus its resources on the development of 177 Lu-PSMA-617 and on a targeted effort to generate proof-of-concept data for the EC17 adaptor-controlled chimeric antigen receptor T-cell (“EC17/CAR T-cell”) program, and to explore out-licensing opportunities for all other development programs, such as EC2629 .

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	2. Significant Accounting Policies Basis of Presentation The accompanying condensed financial statements are prepared in conformity with U.S. generally accepted accounting principles (“GAAP”) for interim financial information to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments, consisting of normal recurring accruals and revisions of estimates, considered necessary for a fair presentation of the accompanying condensed financial statements have been included. Interim results for the three months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2018 or any other future period. These condensed financial statements should be read in conjunction with the Company’s audited financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. Subsequent events have been evaluated through the date of issuance, which is the same as the date this Form 10-Q is filed with the Securities and Exchange Commission (“the SEC”) . Segment Information Operating segments are defined as components of an enterprise engaging in business activities for which discrete financial information is available and regularly reviewed by the chief operating decision maker in deciding how to allocate resources and in assessing performance. All long-lived assets are held in the U.S. The Company views its operations and manages its business in one operating segment . Use of Estimates The preparation of financial statements in conformity with GAAP requires the Company’s management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual amounts may differ from those estimates . Cash and Cash Equivalents The Company considers cash and all highly liquid investments with a maturity of three months or less at the date of purchase to be cash equivalents. Cash equivalents consist primarily of money market instruments, U.S. government treasury obligations, corporate debt securities and repurchase agreements that are maintained by an investment manager . Investments Investments consist primarily of investments in U.S. Treasuries and corporate debt securities, which could also include commercial paper, that are maintained by an investment manager. Management determines the appropriate classification of marketable securities at the time of purchase and reevaluates such classification as of each balance sheet date. Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in other comprehensive income (loss). Realized gains and losses and declines in value judged to be other-than-temporary on available-for-sale securities are included in other income (loss). The Company considers and accounts for other-than-temporary impairments according to the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 320, Investments — Debt and Equity Securities (“ASC 320”). The cost of securities sold is based on the specific-identification method. Discounts and premiums on debt securities are amortized to interest income and expensed over the term of the security . Revenue Recognition Commencing with reporting periods beginning January 1, 2018, the Company recognizes revenue in accordance with ASC 606, Revenue from Contracts with Customers . The Company’s contract revenues consist of revenues from license and collaboration agreements. License and collaboration revenue is primarily generated through agreements with strategic partners for the development and potential commercialization of our product candidates. The terms of the agreement typically include non-refundable upfront fees, funding of research and development activities, payments based upon achievement of milestones and potential royalties on net product sales. Non-refundable upfront fees and funding of research and development activities are considered fixed consideration, while milestone payments and royalties are identified as variable consideration. The Company recognizes revenues from license and collaboration agreements to depict the transfer of promised goods or services in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. In order to determine the appropriate amount of revenue to be recognized as the Company fulfills its obligations under a contract, the Company follows the following steps for in-scope transactions: 1) identification of the contract with a customer, 2) identification of the separate performance obligations in the contract, 3) determination of the transaction price, 4) allocation of the transaction price to the separate performance obligations in the contract, and 5) recognition of revenue when or as the Company satisfies a performance obligation. The Company’s performance obligations may include license rights, research and development services, services associated with regulatory submission and approval processes and services related to potential commercialization processes. Significant judgment may be required to determine the level of effort required under an arrangement and the period over which the Company expects to satisfy its performance obligations under the arrangement. If the Company cannot reasonably estimate when its performance obligations either are satisfied or become inconsequential, then revenue recognition is deferred until the Company can reasonably make such estimates. Revenue is then recognized over the remaining estimated period of performance using the cumulative catch-up method. License Agreements If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, upfront fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that may be bundled with other promises, the Company will utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, upfront fees. Because the drug development process is lengthy and the Company’s collaboration agreements typically cover activities over several years, this approach may result in the deferral of significant amounts of revenue into future periods. Each reporting period, the Company will evaluate the measure of progress and, if necessary, adjust the measure of performance and related revenue recognition. Milestone Payments At the inception of each arrangement that includes milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the value of the associated milestone (such as a regulatory submission by the Company) is included in the transaction price. Milestone payments that are not within the control of the Company, such as approvals from regulators, are not considered probable of being achieved until those approvals are received. When the Company’s assessment of probability of achievement changes and variable consideration becomes probable, any additional estimated consideration is allocated to each performance obligation based on the estimated relative standalone selling prices of the promised good or service underlying each performance obligation and recorded in license, collaboration, and other revenues based upon when the customer obtains control of each element. Royalty Payments For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation to which some or all of the royalty has been allocated has been satisfied. To date, none of the Company’s products have been approved and therefore the Company has not earned any royalty revenue from product sales. Research and Development Expenses Research and development expenses represent costs associated with the ongoing development of novel therapeutics and companion imaging agents for personalized targeted therapies and include salaries and employee benefits, supplies, facility costs related to research activities, and expenses for clinical trials. The Company records accruals for clinical trial expenses based on the estimated amount of work completed. The Company monitors patient enrollment levels and related activities to the extent possible through internal reviews, correspondence, and discussions with research organizations. In the event that a clinical trial is terminated early, the Company records, in the period of termination, an accrual for the estimated remaining costs to complete and close out the trial pursuant to ASC Topic 420, Exit or Disposal Cost Obligations , as a terminated trial does not provide any future economic benefit to the Company. See Note 10 – Restructuring Costs of the Notes to Condensed Financial Statements contained herein for costs incurred during the three months ended March 31, 2018 related to the Company’s restructuring activities . Upfront payments made in connection with business collaborations and research and development arrangements are evaluated under ASC Subtopic 730-20, Research and Development Arrangements . Amounts related to future research and development are capitalized as prepaid research and development and are expensed over the service period based upon the level of services provided. As of March 31, 2018, the Company had approximately $0.6 million of capitalized research and development costs included in prepaid expenses . Acquired In-Process Research and Development Expense The Company has acquired and may continue to acquire the rights to develop and commercialize new drug candidates. In accordance with ASC Subtopic 730-25, Accounting for Research and Development Costs , the upfront payments to acquire a new drug compound, as well as future milestone payments when paid or payable, are immediately expensed as acquired in-process research and development (“IPR&D”) in transactions other than a business combination provided that the drug has not achieved regulatory approval for marketing and, absent obtaining such approval, has no alternative future use. Upon obtaining regulatory approval for marketing, any related milestone payments may be capitalized and amortized over the life of the asset. Stock-Based Compensation The Company accounts for its stock-based compensation pursuant to ASC Topic 718, Compensation — Stock Compensation (“ASC 718”), which requires the recognition of the fair value of stock-based compensation in net income. Stock-based compensation consists of stock options, which are granted at exercise prices at or above the fair market value of the Company’s common stock on the dates of grant, service-based restricted stock units (“RSUs”) and shares available for purchase under the Company’s 2010 Employee Stock Purchase Plan (“ESPP”). For RSUs and stock options issued by the Company, stock-based compensation expense is recognized ratably over the service period . The Company recognizes compensation cost based on the grant date fair value estimated in accordance with the provisions of ASC 718. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method and the if-converted method. For purposes of this calculation, stock options, warrants, RSUs and shares to be purchased under the ESPP are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive . Common stock equivalents As of March 31, 2017 and 2018, the following number of potential common stock equivalents were outstanding: As of March 31, 2017 2018 Outstanding common stock options 6,860,968 5,996,771 Outstanding warrants 34,647 722,000 Outstanding RSUs 616,912 1,524,581 Shares to be purchased under the ESPP 30,121 20,456 Total 7,542,648 8,263,808 These common stock equivalents were excluded from the determination of diluted net loss per share due to their anti-dilutive effect on earnings. The increase in outstanding warrants was due to warrants issued in connection with the License Agreement. For additional information on the outstanding warrants, see Note 8 – Warrants of the Notes to Condensed Financial Statements contained herein.

New Accounting Pronouncements

New Accounting Pronouncements	3 Months Ended
	Mar. 31, 2018
Accounting Changes and Error Corrections [Abstract]
New Accounting Pronouncements	3. New Accounting Pronouncements Recently Issued Accounting Standards In February 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-02, Leases , an update to ASC Topic 842, Leases . This guidance requires lessees to recognize leases as assets and liabilities on their balance sheets but recognize expenses on their income statements in a manner similar to the current accounting guidance. For lessors, the guidance also modifies the classification criteria and the accounting for sales-type and direct finance leases. This update is effective for the Company for interim and annual reporting periods beginning January 1, 2019 unless it elects early adoption. The Company is currently evaluating the impact, if any, the adoption of this guidance will have on its financial statements. Recently Adopted Accounting Standards In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), to clarify the principles used to recognize revenue for all entities. Under ASU 2014-09 as subsequently amended and clarified (“ASC 606”), an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In order to do so, an entity would follow the five-step process for in-scope transactions: 1) identify the contract with a customer, 2) identify the separate performance obligations in the contract, 3) determine the transaction price, 4) allocate the transaction price to the separate performance obligations in the contract, and 5) recognize revenue when (or as) the entity satisfies a performance obligation. ASC 606 was effective for the Company for interim and annual reporting periods beginning January 1, 2018. The Company adopted ASC 606 in the three months ended March 31, 2018 using the modified retrospective method by recognizing the cumulative effect of initially applying the new revenue standard as an adjustment to the opening balance of retained deficit. The cumulative effect related to the adoption of ASC 606 was a $0.3 million decrease to the opening balance of retained deficit at January 1, 2018. The Company had deferred revenue related to its agreement with Nihon Medi-Physic Co., LTD. (“NMP”) of approximately $0.4 million at March 31, 2018 and will record the revenue on a straight-line basis over the remaining estimated performance obligation period of approximately six years. The Company currently has a limited number of contracts with customers and only one revenue stream, which relates to collaboration and licensing arrangements, and which represents all of the revenue earned in the three months ended March 31, 2018. The adoption of ASC 606 did not have a material impact on the Company’s financial statements and is not expected to have a material impact on the Company’s financial statements on an ongoing basis.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Other Comprehensive Income (Loss)	4. Other Comprehensive Income (Loss) The following tables summarize the accumulated balances related to each component of other comprehensive loss for the three months ended March 31, 2017 and 2018: Accumulated Unrealized Net Other Losses Comprehensive on Securities Losses Balance at December 31, 2016 $ (41,196) $ (41,196) Unrealized loss (12,681) (12,681) Other comprehensive loss (12,681) (12,681) Balance at March 31, 2017 $ (53,877) $ (53,877) Accumulated Unrealized Net Other Losses Comprehensive on Securities Losses Balance at December 31, 2017 $ (64,433) $ (64,433) Unrealized loss (14,710) (14,710) Other comprehensive loss (14,710) (14,710) Balance at March 31, 2018 $ (79,143) $ (79,143)

Investments

Investments	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investments	5. Investments The Company applies the fair value measurement and disclosure provisions of ASC Topic 820, Fair Value Measurements and Disclosures (“ASC 820”). ASC 820, which defines fair value, establishes a framework for measuring fair value in GAAP, and expands disclosures about fair value measurements. Investments consist primarily of investments with maturities greater than three months, but no longer than 24 months, when purchased . ASC 820 establishes a three-level valuation hierarchy for fair value measurements. These valuation techniques are based upon the transparency of inputs (observable and unobservable) to the valuation of an asset or liability as of the measurement date. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect the Company’s market assumptions. These two types of inputs create the following fair value hierarchy : Level 1 — Valuation is based on quoted prices for identical assets or liabilities in active markets. Level 2 — Valuation is based on quoted prices for similar assets or liabilities in active markets, or other inputs that are observable for the asset or liability, either directly or indirectly, for the full term of the financial instrument. Level 3 — Valuation is based upon other unobservable inputs that are significant to the fair value measurement. The fair value of the Company’s fixed income securities is based on a market approach using quoted market values. The following table summarizes the fair value of cash and cash equivalents and investments as of December 31, 2017: Fair Value Description Cost Level 1 Level 2 (Carrying Value) Cash Cash $ 2,544,972 $ 2,544,972 $ — $ 2,544,972 Cash equivalents (maturity of 3 months or less) Repurchase agreements 10,000,000 — 10,000,000 10,000,000 Money market funds 6,014,158 6,014,158 — 6,014,158 Cash and cash equivalents $ 18,559,130 $ 8,559,130 $ 10,000,000 $ 18,559,130 Short-term investments (due within 1 year) U.S. government treasury obligations $ 63,034,548 $ 62,970,115 $ — $ 62,970,115 Corporate obligations 15,942,182 — 15,942,182 15,942,182 Total short-term investments $ 78,976,730 $ 62,970,115 $ 15,942,182 $ 78,912,297 The following table summarizes the fair value of cash and cash equivalents and investments as of March 31, 2018: Fair Value Description Cost Level 1 Level 2 (Carrying Value) Cash Cash $ 8,423,398 $ 8,423,398 $ — $ 8,423,398 Cash equivalents (maturity of 3 months or less) Repurchase agreements 10,000,000 — 10,000,000 10,000,000 Money market funds 16,993,446 — 16,993,446 U.S. government treasury obligations 34,955,020 34,956,700 — 34,956,700 Corporate obligations 19,459,253 — 19,458,200 19,458,200 Cash and cash equivalents $ 89,831,117 $ 60,373,544 $ 29,458,200 $ 89,831,744 Short-term investments (due within 1 year) U.S. government treasury obligations $ 56,621,253 $ 56,550,250 $ — $ 56,550,250 Corporate obligations 26,751,400 — 26,742,633 26,742,633 Total short-term investments $ 83,372,653 $ 56,550,250 $ 26,742,633 $ 83,292,883 All securities held at December 31, 2017 and March 31, 2018, were classified as available-for-sale as defined by ASC 320. Total unrealized gross gains were $1,756 as of March 31, 2018. There were no unrealized gross gains as of December 31, 2017. Total unrealized gross losses were $64,433 and $80,899 as of December 31, 2017 and March 31, 2018, respectively. The Company does not consider any of the unrealized losses to be other-than-temporary impairments because the Company has the intent and ability to hold investments until they recover in value. There were no total realized gross gains or total realized gross losses for the three months ended March 31, 2017 and 2018.

Collaborations and Other Arrang

Collaborations and Other Arrangements	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborations	6. Collaboration and Other Arrangements ABX Development and License Agreement In September 2017, the Company entered into the License Agreement with ABX that grants the Company exclusive worldwide rights to develop and commercialize PSMA-617 agents. Under the terms of the License Agreement, the Company will be responsible for, and bear the future costs of, worldwide development and commercialization of PSMA-617. As consideration for the exclusive license, the Company made an upfront cash payment on September 29, 2017 of approximately $11.9 million to ABX, consisting of $12.0 million less an immaterial expense reimbursement amount, and issued to ABX 2,000,000 shares of the Company’s common stock (see Note 7 – Stockholders’ Equity (Deficit) of the Notes to Condensed Financial Statements for additional information regarding this issuance) and two warrants to purchase, in the aggregate, 4,000,000 shares of the Company’s common stock (see Note 8 – Warrants of the Notes to Condensed Financial Statements for additional information regarding the warrants). The License Agreement also obligates the Company to pay ABX regulatory milestone payments of up to $25.0 million, sales milestone payments of up to $135.0 million, and tiered royalties, beginning in the mid-teens and not to exceed the mid-twenties, based on percentages of net sales . In addition, under a three-party agreement, entered into in October 2017, among the Company, the University of Sydney (the “University”) and ANZUP, a cooperative cancer trials group operating in Australia and New Zealand pursuing research in genito-urinary malignancies, ANZUP sponsors jointly with the University a randomized phase 2 multi-center TheraP trial of 177 Lu-PSMA-617 versus cabazitaxel in 200 mCRPC patients. The TheraP trial commenced enrollment in the first quarter of 2018. Under the three-party agreement, the Company provides the PSMA-617 precursor molecule and financial support for the trial. The Company will have access to data generated from the trial, which is a potentially important supportive trial for future regulatory submissions. The primary financial obligations of the trial, along with labeling PSMA-617 with Lutetium-177, will be the responsibility of the University and ANZUP . NMP License and Commercialization Agreement In August 2013, the Company entered into a license and commercialization agreement with NMP that grants NMP the right to develop and commercialize etarfolatide in Japan for use in connection with any folate receptor-targeted therapeutic drug in Japan. The Company received a $1.0 million non-refundable upfront payment, is eligible for up to $4.5 million based on the successful achievement of regulatory goals for etarfolatide in five different cancer indications and is eligible to receive double-digit percentage royalties on sales of etarfolatide in Japan. For revenue recognition purposes, the Company historically viewed the agreement with NMP as a multiple element arrangement upon execution of the agreement in 2013. The Company’s deliverables were accounted for as a single unit of account, therefore the non-refundable upfront payment was being recognized on a straight-line basis over the performance period which had been determined to continue through the estimated termination date of the contract, or through the end of 2033. In the three months ended March 31, 2018, the Company adopted ASC 606 and therefore analyzed the agreement with NMP using the five-step process as described in Note 3 – New Accounting Pronouncements of the Notes to Condensed Financial Statements contained herein. The Company determined that the upfront payment of $1.0 million relates to one performance obligation, which was determined to be the successful development and commercialization of etarfolatide in connection with a related folate receptor-targeted therapeutic drug in Japan, and should be allocated over the performance period that the Company estimates will be required to satisfy the combined performance obligation rather than the period over which the final undelivered item was estimated to be delivered, which was the life of the contract, under the previous standard. Under the modified retrospective method of adoption of ASC 606, t he Company recorded a cumulative effect adjustment to reduce deferred revenue by $0.3 million and to decrease its retained deficit at January 1, 2018. The Company had deferred revenue related to the agreement with NMP of approximately $0.4 million at March 31, 2018 and will continue to record the revenue on a straight-line basis over the remaining estimated performance obligation period of approximately six years. The adoption of ASC 606 did not have a material effect on the Company’s financial statements. The arrangement with NMP includes milestone payments of up to approximately $4.5 million and the milestones are based on the commencement of clinical trials in Japan for specific and non-specific indications and filing for approval in Japan for specific and non-specific indications. The Company evaluated each of these milestone payments and believes that all of the milestones should be excluded from the transaction price due to substantial performance risk. In order for the milestones to be reached, the Company must complete additional clinical trials which show a positive outcome or receive approval from a regulatory authority. To date, the products have not been approved in Japan and no revenue has been recognized related to the regulatory milestones or royalties. NMP has the right to terminate the collaboration agreement on 90 days notice prior to the first commercial sale in Japan and six months notice after the first commercial sale in Japan. NMP also has the right to terminate the agreement on six months notice if the Company fails to launch any folate receptor-targeted therapeutic drug after receiving regulatory approval in Japan. NMP and the Company each have the right to terminate the agreement due to the material breach or insolvency of the other party. Upon termination of the agreement depending on the circumstances, the parties have varying rights and obligations with respect to licensing and related regulatory materials and data.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Stockholders' Equity (Deficit)	7. Stockholders’ Equity (Deficit) Public Offering of Common Stock On March 2, 2018, the Company closed an underwritten registered public offering of 20,535,714 shares of its common stock, which included the underwriters’ exercise in full of their option to purchase additional shares. The shares were sold at a public offering price of $4. 20 per share. In the three months ended March 31, 2018, the Company received aggregate net proceeds from the offering of approximately $80.9 million, after deducting underwriting discounts and commissions of $5.2 million and offering expenses paid by the Company of $0.1 million. Issuances Related to the License Agreement In connection with the License Agreement, the Company issued to ABX on September 29, 2017, 2,000,000 unregistered shares of the Company’s common stock and two warrants to purchase up to 4,000,000 shares of the Company’s common stock, one of which warrants to purchase 3,278,000 shares was exercised on that same day. Pursuant to a Registration Rights Agreement entered into with ABX, the Company registered for resale these 6,000,000 shares of common stock with the SEC on a Form S-3 Registration Statement that was declared effective on October 24, 2017 . Stock-Based Compensation Plans The Company has had stock-based compensation plans since 1997. The awards made under the plans adopted in 1997 and 2007 consisted of stock options. The 2010 Equity Incentive Plan (the “2010 Plan”), which is the only plan under which awards may currently be made, authorizes awards in the form of stock options, stock appreciation rights, restricted stock, RSUs, performance-based RSUs and performance units and performance shares. Awards under the 2010 Plan may be made to employees, directors and certain consultants as determined by the compensation committee of the board of directors. There were 11,850,563 and 13,296,563 shares of common stock authorized and reserved under these plans at December 31, 2017 and March 31, 2018, respectively . Stock Options Under the various plans, employees have been granted incentive stock options, while directors and consultants have been granted non-qualified options. The plans allow the holder of an option to purchase common stock at the exercise price, which was at or above the fair value of the Company’s common stock on the date of grant . Generally, options granted under the 1997 and 2007 plans in connection with an employee’s commencement of employment vested over a four-year period with one-half of the shares subject to the grant vesting after two years of employment and the remaining options vesting monthly over the remainder of the four-year period. Options granted under the 1997 and 2007 plans for performance or promotions vested monthly over a four-year period. Generally, options granted under the 2010 Plan vest annually over a three-year or four-year period. Unexercised stock options terminate on the tenth anniversary date after the date of grant. The Company recognizes stock-based compensation expense over the requisite service period of the individual grantees, which generally equals the vesting period. The Company utilizes a Black-Scholes option-pricing model to estimate the value of stock options. The Black-Scholes model allows the use of a range of assumptions related to historical volatility, risk-free interest rate, employee exercise behavior and dividend yield. The Company is using the “simplified” method for “plain vanilla” options to estimate the expected term of the stock option grants. Under this approach, the weighted-average expected life is presumed to be the average of the vesting term and the contractual term of the option. The risk-free interest rate assumption is derived from the weighted-average yield of a U.S. Treasury security with the same term as the expected life of the options, and the dividend yield assumption is based on historical experience and the Company’s estimate of future dividend yields . The weighted-average value of the individual options granted during the three months ended March 31, 2017 and 2018 were determined using the following assumptions. Three Months Ended March 31, 2017 2018 Expected volatility % 102.03 % Risk-free interest rate 2.12 % 2.65 % Weighted-average expected life (in years) 6.3 6.4 Dividend yield % % The Company’s stock option activity and related information are summarized as follows: Weighted-Average Remaining Weighted-Average Contractual Term Aggregate Options Exercise Price (In Years) Intrinsic Value Outstanding at January 1, 2018 5,878,660 $ 5.93 Granted during period 688,192 3.07 Exercised during period (561,088) 4.10 Expired during period (8,993) 3.06 Outstanding at March 31, 2018 5,996,771 $ 5.78 6.18 $ 22,125,418 Exercisable at March 31, 2018 4,290,445 $ 6.92 5.02 $ 11,551,954 As of March 31, 2018, the total remaining unrecognized compensation cost related to stock options granted was $3.4 million, which is expected to be recognized over a weighted average period of approximately 2.0 years. Restricted Stock Units RSUs are service-based awards that will vest and be paid in the form of one share of the Company’s common stock for each RSU, generally in two, three or four equal annual installments beginning on the first anniversary of the date of grant of an RSU. As of March 31, 2018, the Company had 1,524,581 RSU awards outstanding. As of March 31, 2018, the total remaining unrecognized compensation cost related to RSUs was $5.7 million, which is expected to be recognized over a weighted average period of approximately 1.4 years. The following table sets forth the number of RSUs that were granted, vested and forfeited in the period indicated: Restricted Weighted-Average Stock Grant Units Date Fair Value Outstanding at January 1, 2018 1,383,770 $ 5.05 Granted during period 301,958 3.02 Vested during period (161,147) 4.27 Outstanding at March 31, 2018 1,524,581 $ 4.73 Employee Stock Purchase Plan At January 1, 2018, 769,542 common shares were available for issuance under the ESPP. Shares may be issued under the ESPP twice a year. There were no purchases in the three months ended March 31, 2018. At March 31, 2018, there were 769,542 common shares available for issuance under the ESPP.

Warrants

Warrants	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Warrant Disclosure [Text Block]	8. Warrants In connection with the License Agreement, the Company issued to ABX on September 29, 2017, two warrants to purchase up to 4,000,000 shares of the Company’s common stock, at a per share exercise price of $1.39, which is equal to the average closing price of the Company’s common stock during the 30 calendar days prior to September 29 , 2017. The Company accounted for the warrants at fair value in stockholders’ equity. The warrants contain a conversion feature in the case of certain mergers or consolidations by the Company. Immediately upon issuance, ABX assigned the warrants to an affiliate and certain related parties, which exercised a warrant for 3,278,000 shares on September 29, 2017, resulting in proceeds to the Company in the amount of approximately $4.6 million. The remaining warrant, covering an aggregate of 722,000 shares, remained outstanding as of March 31, 2018, is exercisable until September 29, 2027, and is subject to restrictions on transfer. This warrant was valued using the Black-Scholes model utilizing a ten-year term, the Company’s historic volatility of 91.1%, and an interest rate of 2.28% which is the risk free interest rate of a treasury bond with the same term as the warrants, which are level 2 fair value measurements. There were no other outstanding warrants as of March 31, 2018 .

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes The Company accounts for income taxes under the liability method in accordance with the provisions of ASC Topic 740, Income Taxes . The Company recognizes future tax benefits, such as net operating losses, to the extent those benefits are expected to be realized in future periods. Due to uncertainty surrounding the realization of its deferred tax assets, the Company has recorded a valuation allowance against its net deferred tax assets. The Company experienced a change in ownership as defined under Section 382 of the U.S. Internal Revenue Code (the “Code”) in August 2011. As a result, the future use of its net operating losses and credit equivalents, after giving effect to net unrealized built-in gains, were previously limited, but the limitations associated with the change in ownership in August 2011 ended as of December 31, 2017. All amounts are available for use if the Company generates future taxable income prior to expiration of the net operating losses, which will begin in 2021. The utilization of the net operating loss carryforwards could be limited beyond the Company's generation of taxable income if an additional change in the underlying ownership of the Company's common stock has occurred, resulting in a limitation on the amounts that could be utilized in any given period under Section 382 of the Code. On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act (the “2017 Tax Act”) which, among other provisions, reduces the corporate income tax rate from 35% to 21% effective January 1, 2018. The Company’s estimate of the impacts of the 2017 Tax Act are provisional and are based upon its analysis and interpretations of currently available information. Uncertainties remain regarding the impact of the 2017 Tax Act due to future regulatory and rulemaking processes, prospects of additional corrective or supplemental legislation, and potential trade or other litigation. These uncertainties, along with the Company’s completion of the calculations and potential changes in its initial assumptions as new information becomes available, could cause the actual charge to ultimately differ from the provisional amount recorded in 2017 related to the enactment of the 2017 Tax Act. All provisional amounts recorded by the Company are fully reserved.

Restructuring Costs

Restructuring Costs	3 Months Ended
	Mar. 31, 2018
Restructuring Costs [Abstract]
Restructuring and Related Activities Disclosure [Text Block]	10. Restructuring Costs In June 2017, the Company refocused its clinical development efforts and aligned its resources to focus on the Company’s highest value opportunities while maintaining key capabilities. The Company’s restructuring activities included a reduction of its workforce by approximately 40%, as well as stopping enrollment in its EC1456 phase 1b trial as the assessment of trial data did not yield the level of clinical activity necessary to support continued advancement of EC1456. In December 2017, the Company stopped enrollment in its EC1456 ovarian cancer surgical trial. Pursuant to ASC Topic 420, Exit or Disposal Cost Obligations , the Company recorded $2.3 million of restructuring expenses in the second quarter of 2017 as follows: · included in research and development expenses were expenses for employee termination benefits of $0.9 million, $0.9 million for the remaining EC1456 phase 1b trial expenses, including site close-out expenses, $0.3 million related to other restructuring expenses, and $0.1 million related to fixed asset impairment charges; and · included in general and administrative expenses were expenses for employee termination benefits of $0.1 million. As of March 31, 2018, the Company had paid all severance and other costs related to the restructuring activities, and had a clinical trial accrual balance related to the EC1456 phase 1b trial termination of $23,300, which is expected to be fully paid by the end of the second quarter of 2018 . The following table summarizes the remaining restructuring accruals for the three months ended March 31, 2018: EC1456 Phase 1b Trial Termination Accrual Balance, January 1, 2018 $ 106,900 Amounts paid in the three months ended March 31, 2018 (83,600) Balance, March 31, 2018 $ 23,300

Significant Accounting Polici17

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed financial statements are prepared in conformity with U.S. generally accepted accounting principles (“GAAP”) for interim financial information to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments, consisting of normal recurring accruals and revisions of estimates, considered necessary for a fair presentation of the accompanying condensed financial statements have been included. Interim results for the three months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2018 or any other future period. These condensed financial statements should be read in conjunction with the Company’s audited financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. Subsequent events have been evaluated through the date of issuance, which is the same as the date this Form 10-Q is filed with the Securities and Exchange Commission (“the SEC”) .
Segment Information	Segment Information Operating segments are defined as components of an enterprise engaging in business activities for which discrete financial information is available and regularly reviewed by the chief operating decision maker in deciding how to allocate resources and in assessing performance. All long-lived assets are held in the U.S. The Company views its operations and manages its business in one operating segment .
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires the Company’s management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual amounts may differ from those estimates .
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers cash and all highly liquid investments with a maturity of three months or less at the date of purchase to be cash equivalents. Cash equivalents consist primarily of money market instruments, U.S. government treasury obligations, corporate debt securities and repurchase agreements that are maintained by an investment manager .
Investments	Investments Investments consist primarily of investments in U.S. Treasuries and corporate debt securities, which could also include commercial paper, that are maintained by an investment manager. Management determines the appropriate classification of marketable securities at the time of purchase and reevaluates such classification as of each balance sheet date. Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in other comprehensive income (loss). Realized gains and losses and declines in value judged to be other-than-temporary on available-for-sale securities are included in other income (loss). The Company considers and accounts for other-than-temporary impairments according to the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 320, Investments — Debt and Equity Securities (“ASC 320”). The cost of securities sold is based on the specific-identification method. Discounts and premiums on debt securities are amortized to interest income and expensed over the term of the security .
Revenue Recognition	Revenue Recognition Commencing with reporting periods beginning January 1, 2018, the Company recognizes revenue in accordance with ASC 606, Revenue from Contracts with Customers . The Company’s contract revenues consist of revenues from license and collaboration agreements. License and collaboration revenue is primarily generated through agreements with strategic partners for the development and potential commercialization of our product candidates. The terms of the agreement typically include non-refundable upfront fees, funding of research and development activities, payments based upon achievement of milestones and potential royalties on net product sales. Non-refundable upfront fees and funding of research and development activities are considered fixed consideration, while milestone payments and royalties are identified as variable consideration. The Company recognizes revenues from license and collaboration agreements to depict the transfer of promised goods or services in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. In order to determine the appropriate amount of revenue to be recognized as the Company fulfills its obligations under a contract, the Company follows the following steps for in-scope transactions: 1) identification of the contract with a customer, 2) identification of the separate performance obligations in the contract, 3) determination of the transaction price, 4) allocation of the transaction price to the separate performance obligations in the contract, and 5) recognition of revenue when or as the Company satisfies a performance obligation. The Company’s performance obligations may include license rights, research and development services, services associated with regulatory submission and approval processes and services related to potential commercialization processes. Significant judgment may be required to determine the level of effort required under an arrangement and the period over which the Company expects to satisfy its performance obligations under the arrangement. If the Company cannot reasonably estimate when its performance obligations either are satisfied or become inconsequential, then revenue recognition is deferred until the Company can reasonably make such estimates. Revenue is then recognized over the remaining estimated period of performance using the cumulative catch-up method. License Agreements If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, upfront fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that may be bundled with other promises, the Company will utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, upfront fees. Because the drug development process is lengthy and the Company’s collaboration agreements typically cover activities over several years, this approach may result in the deferral of significant amounts of revenue into future periods. Each reporting period, the Company will evaluate the measure of progress and, if necessary, adjust the measure of performance and related revenue recognition. Milestone Payments At the inception of each arrangement that includes milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the value of the associated milestone (such as a regulatory submission by the Company) is included in the transaction price. Milestone payments that are not within the control of the Company, such as approvals from regulators, are not considered probable of being achieved until those approvals are received. When the Company’s assessment of probability of achievement changes and variable consideration becomes probable, any additional estimated consideration is allocated to each performance obligation based on the estimated relative standalone selling prices of the promised good or service underlying each performance obligation and recorded in license, collaboration, and other revenues based upon when the customer obtains control of each element. Royalty Payments For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation to which some or all of the royalty has been allocated has been satisfied. To date, none of the Company’s products have been approved and therefore the Company has not earned any royalty revenue from product sales.
Research and Development Expenses	Research and Development Expenses Research and development expenses represent costs associated with the ongoing development of novel therapeutics and companion imaging agents for personalized targeted therapies and include salaries and employee benefits, supplies, facility costs related to research activities, and expenses for clinical trials. The Company records accruals for clinical trial expenses based on the estimated amount of work completed. The Company monitors patient enrollment levels and related activities to the extent possible through internal reviews, correspondence, and discussions with research organizations. In the event that a clinical trial is terminated early, the Company records, in the period of termination, an accrual for the estimated remaining costs to complete and close out the trial pursuant to ASC Topic 420, Exit or Disposal Cost Obligations , as a terminated trial does not provide any future economic benefit to the Company. See Note 10 – Restructuring Costs of the Notes to Condensed Financial Statements contained herein for costs incurred during the three months ended March 31, 2018 related to the Company’s restructuring activities . Upfront payments made in connection with business collaborations and research and development arrangements are evaluated under ASC Subtopic 730-20, Research and Development Arrangements . Amounts related to future research and development are capitalized as prepaid research and development and are expensed over the service period based upon the level of services provided. As of March 31, 2018, the Company had approximately $0.6 million of capitalized research and development costs included in prepaid expenses .
Acquired In-Process Research and Development Expense	Acquired In-Process Research and Development Expense The Company has acquired and may continue to acquire the rights to develop and commercialize new drug candidates. In accordance with ASC Subtopic 730-25, Accounting for Research and Development Costs , the upfront payments to acquire a new drug compound, as well as future milestone payments when paid or payable, are immediately expensed as acquired in-process research and development (“IPR&D”) in transactions other than a business combination provided that the drug has not achieved regulatory approval for marketing and, absent obtaining such approval, has no alternative future use. Upon obtaining regulatory approval for marketing, any related milestone payments may be capitalized and amortized over the life of the asset.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for its stock-based compensation pursuant to ASC Topic 718, Compensation — Stock Compensation (“ASC 718”), which requires the recognition of the fair value of stock-based compensation in net income. Stock-based compensation consists of stock options, which are granted at exercise prices at or above the fair market value of the Company’s common stock on the dates of grant, service-based restricted stock units (“RSUs”) and shares available for purchase under the Company’s 2010 Employee Stock Purchase Plan (“ESPP”). For RSUs and stock options issued by the Company, stock-based compensation expense is recognized ratably over the service period . The Company recognizes compensation cost based on the grant date fair value estimated in accordance with the provisions of ASC 718.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method and the if-converted method. For purposes of this calculation, stock options, warrants, RSUs and shares to be purchased under the ESPP are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive . Common stock equivalents As of March 31, 2017 and 2018, the following number of potential common stock equivalents were outstanding: As of March 31, 2017 2018 Outstanding common stock options 6,860,968 5,996,771 Outstanding warrants 34,647 722,000 Outstanding RSUs 616,912 1,524,581 Shares to be purchased under the ESPP 30,121 20,456 Total 7,542,648 8,263,808 These common stock equivalents were excluded from the determination of diluted net loss per share due to their anti-dilutive effect on earnings. The increase in outstanding warrants was due to warrants issued in connection with the License Agreement. For additional information on the outstanding warrants, see Note 8 – Warrants of the Notes to Condensed Financial Statements contained herein.

Significant Accounting Polici18

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Schedule of common stock equivalents excluded due to anti-dilutive effect	As of March 31, 2017 2018 Outstanding common stock options 6,860,968 5,996,771 Outstanding warrants 34,647 722,000 Outstanding RSUs 616,912 1,524,581 Shares to be purchased under the ESPP 30,121 20,456 Total 7,542,648 8,263,808

Other Comprehensive Income (L19

Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2018
Other Comprehensive Income (Loss), Tax [Abstract]
Schedule of components of other comprehensive income	The following tables summarize the accumulated balances related to each component of other comprehensive loss for the three months ended March 31, 2017 and 2018: Accumulated Unrealized Net Other Losses Comprehensive on Securities Losses Balance at December 31, 2016 $ (41,196) $ (41,196) Unrealized loss (12,681) (12,681) Other comprehensive loss (12,681) (12,681) Balance at March 31, 2017 $ (53,877) $ (53,877) Accumulated Unrealized Net Other Losses Comprehensive on Securities Losses Balance at December 31, 2017 $ (64,433) $ (64,433) Unrealized loss (14,710) (14,710) Other comprehensive loss (14,710) (14,710) Balance at March 31, 2018 $ (79,143) $ (79,143)

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Schedule of the fair value of cash and cash equivalents and investments	The following table summarizes the fair value of cash and cash equivalents and investments as of December 31, 2017: Fair Value Description Cost Level 1 Level 2 (Carrying Value) Cash Cash $ 2,544,972 $ 2,544,972 $ — $ 2,544,972 Cash equivalents (maturity of 3 months or less) Repurchase agreements 10,000,000 — 10,000,000 10,000,000 Money market funds 6,014,158 6,014,158 — 6,014,158 Cash and cash equivalents $ 18,559,130 $ 8,559,130 $ 10,000,000 $ 18,559,130 Short-term investments (due within 1 year) U.S. government treasury obligations $ 63,034,548 $ 62,970,115 $ — $ 62,970,115 Corporate obligations 15,942,182 — 15,942,182 15,942,182 Total short-term investments $ 78,976,730 $ 62,970,115 $ 15,942,182 $ 78,912,297 The following table summarizes the fair value of cash and cash equivalents and investments as of March 31, 2018: Fair Value Description Cost Level 1 Level 2 (Carrying Value) Cash Cash $ 8,423,398 $ 8,423,398 $ — $ 8,423,398 Cash equivalents (maturity of 3 months or less) Repurchase agreements 10,000,000 — 10,000,000 10,000,000 Money market funds 16,993,446 — 16,993,446 U.S. government treasury obligations 34,955,020 34,956,700 — 34,956,700 Corporate obligations 19,459,253 — 19,458,200 19,458,200 Cash and cash equivalents $ 89,831,117 $ 60,373,544 $ 29,458,200 $ 89,831,744 Short-term investments (due within 1 year) U.S. government treasury obligations $ 56,621,253 $ 56,550,250 $ — $ 56,550,250 Corporate obligations 26,751,400 — 26,742,633 26,742,633 Total short-term investments $ 83,372,653 $ 56,550,250 $ 26,742,633 $ 83,292,883

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Schedule of weighted-average valuation assumptions	Three Months Ended March 31, 2017 2018 Expected volatility % 102.03 % Risk-free interest rate 2.12 % 2.65 % Weighted-average expected life (in years) 6.3 6.4 Dividend yield % %
Schedule of stock option activity	Weighted-Average Remaining Weighted-Average Contractual Term Aggregate Options Exercise Price (In Years) Intrinsic Value Outstanding at January 1, 2018 5,878,660 $ 5.93 Granted during period 688,192 3.07 Exercised during period (561,088) 4.10 Expired during period (8,993) 3.06 Outstanding at March 31, 2018 5,996,771 $ 5.78 6.18 $ 22,125,418 Exercisable at March 31, 2018 4,290,445 $ 6.92 5.02 $ 11,551,954
Schedule of restricted stock unit activity	Restricted Weighted-Average Stock Grant Units Date Fair Value Outstanding at January 1, 2018 1,383,770 $ 5.05 Granted during period 301,958 3.02 Vested during period (161,147) 4.27 Outstanding at March 31, 2018 1,524,581 $ 4.73

Nature of Business and Organi22

Nature of Business and Organization (Details)	1 Months Ended
	Sep. 30, 2017personitem
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of interim assessments in trial | item	2
Number of patients with progressive PSMA-positive metastatic castration-resistant prostrate cancer | person	750

Significant Accounting Polici23

Significant Accounting Policies (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)segment
Research and Development Expense
Capitalized research and development costs | $	$ 0.6
Segment Information
Number of Operating Segments | segment	1

Significant Accounting Polici24

Significant Accounting Policies - Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Common stock equivalents
Antidilutive securities excluded from computation of earnings per share	8,263,808	7,542,648
Outstanding common stock options
Common stock equivalents
Antidilutive securities excluded from computation of earnings per share	5,996,771	6,860,968
Outstanding warrants
Common stock equivalents
Antidilutive securities excluded from computation of earnings per share	722,000	34,647
RSUs
Common stock equivalents
Antidilutive securities excluded from computation of earnings per share	1,524,581	616,912
Shares to be purchased under the ESPP
Common stock equivalents
Antidilutive securities excluded from computation of earnings per share	20,456	30,121

New Accounting Pronouncements (

New Accounting Pronouncements (Details)	3 Months Ended
	Mar. 31, 2018USD ($)item	Dec. 31, 2017USD ($)
New Accounting Pronouncement or Change in Accounting Principle, Retrospective Adjustments [Abstract]
Deferred revenue, net of current portion | $	$ 363,266	$ 731,944
Performance obligation period of recognition	6 years
Number of revenue streams | item	1

Other Comprehensive Income (L26

Other Comprehensive Income (Loss) - components (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 95,484,145
Balance at end of period	171,701,887
Unrealized Net Gains (Losses) on Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(64,433)	$ (41,196)
Unrealized gain (loss)	(14,710)	(12,681)
Other comprehensive income (loss)	(14,710)	(12,681)
Balance at end of period	(79,143)	(53,877)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(64,433)	(41,196)
Unrealized gain (loss)	(14,710)	(12,681)
Other comprehensive income (loss)	(14,710)	(12,681)
Balance at end of period	$ (79,143)	$ (53,877)

Investments (Details)

Investments (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Cash
Cash	$ 8,423,398	$ 2,544,972
Cash equivalents
Cash and cash equivalents at carrying value	89,831,744	18,559,130	$ 33,660,918	$ 31,228,192
Short-term Investments
Short-term investments (due within 1 year)
Available-for-sale securities, amortized cost	83,372,653	78,976,730
Available-for-sale securities	83,292,883	78,912,297
Short-term Investments | U.S. government treasury obligations
Short-term investments (due within 1 year)
Available-for-sale securities, amortized cost	56,621,253	63,034,548
Available-for-sale securities	56,550,250	62,970,115
Short-term Investments | Corporate obligations
Short-term investments (due within 1 year)
Available-for-sale securities, amortized cost	26,751,400	15,942,182
Available-for-sale securities	26,742,633	15,942,182
Cash Equivalents [Member]
Cash equivalents
Cash and cash equivalents at cost	89,831,117	18,559,130
Cash and cash equivalents at carrying value	89,831,744	18,559,130
FDIC insured deposits and money market funds
Cash equivalents
Cash equivalents at cost		10,000,000
Cash Equivalents, at Carrying Value		10,000,000
Repurchase Agreements
Cash equivalents
Cash equivalents at cost	10,000,000
Cash Equivalents, at Carrying Value	10,000,000
Money Market Funds
Cash equivalents
Cash equivalents at cost	16,993,446	6,014,158
Cash Equivalents, at Carrying Value	16,993,446	6,014,158
U.S. government treasury obligations
Cash equivalents
Cash equivalents at cost	34,955,020
Cash Equivalents, at Carrying Value	34,956,700
Corporate obligations
Cash equivalents
Cash equivalents at cost	19,459,253
Cash Equivalents, at Carrying Value	19,458,200
Level 1
Cash
Cash	8,423,398	2,544,972
Level 1 | Short-term Investments
Short-term investments (due within 1 year)
Available-for-sale securities	56,550,250	62,970,115
Level 1 | Short-term Investments | U.S. government treasury obligations
Short-term investments (due within 1 year)
Available-for-sale securities	56,550,250	62,970,115
Level 1 | Cash Equivalents [Member]
Cash equivalents
Cash and cash equivalents at carrying value	60,373,544	8,559,130
Level 1 | Money Market Funds
Cash equivalents
Cash Equivalents, at Carrying Value	16,993,446	6,014,158
Level 1 | U.S. government treasury obligations
Cash equivalents
Cash Equivalents, at Carrying Value	34,956,700
Level 2 | Short-term Investments
Short-term investments (due within 1 year)
Available-for-sale securities	26,742,633	15,942,182
Level 2 | Short-term Investments | Corporate obligations
Short-term investments (due within 1 year)
Available-for-sale securities	26,742,633	15,942,182
Level 2 | Cash Equivalents [Member]
Cash equivalents
Cash and cash equivalents at carrying value	29,458,200	10,000,000
Level 2 | FDIC insured deposits and money market funds
Cash equivalents
Cash Equivalents, at Carrying Value		$ 10,000,000
Level 2 | Repurchase Agreements
Cash equivalents
Cash Equivalents, at Carrying Value	10,000,000
Level 2 | Corporate obligations
Cash equivalents
Cash Equivalents, at Carrying Value	$ 19,458,200

Investments unrealized gains (D

Investments unrealized gains (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Unrealized gain on securities	$ 1,756		$ 0
Unrealized loss on securities	80,899		64,433
Realized gain on securities	0	$ 0
Realized loss on securities	$ 0		$ 0

Collaborations and Other Arra29

Collaborations and Other Arrangements - ABX (Details) $ in Millions	Sep. 29, 2017USD ($)itemshares	Oct. 31, 2017person	Sep. 30, 2017person	Mar. 31, 2018item
ABX Development and License Agreement
Number of patients with mCRPC included in study | person			750
ABX | License Agreement
ABX Development and License Agreement
Upfront cash payment	$ 11.9
Total consideration excluding common stock shares and warrants	$ 12
Issuance of common stock in connection with development and license agreement (in shares) | shares	2,000,000
Number of warrants issued per agreement | item	2
Aggregate number of common stock shares that may be purchased by exercise of warrants | shares	4,000,000
ABX | Maximum | License Agreement
ABX Development and License Agreement
Aggregate number of common stock shares that may be purchased by exercise of warrants | shares	4,000,000
ABX | Achievement Of Regulatory Milestones | License Agreement
ABX Development and License Agreement
Potential milestone payments to be paid	$ 25
ABX | Achievement Of Sales Milestones | License Agreement
ABX Development and License Agreement
Potential milestone payments to be paid	$ 135
University of Sydney | Anzup | Three Party Agreement [Member]
ABX Development and License Agreement
Number of parties in the agreement | item				3
Number of patients with mCRPC included in study | person		200

Collaborations and Other Arra30

Collaborations and Other Arrangements - NMP (Details)	1 Months Ended	3 Months Ended	56 Months Ended
	Aug. 31, 2013USD ($)item	Mar. 31, 2018USD ($)	Mar. 31, 2018USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)
NMP License and Commercialization Agreement
Retained deficit		$ (317,217,775)	$ (317,217,775)		$ (308,954,535)
Performance obligation period of recognition		6 years
Deferred revenue		$ 363,266	363,266		$ 731,944
ASU 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
NMP License and Commercialization Agreement
Retained deficit				$ 300,000
Deferred revenue				$ (300,000)
NMP | License And Commercialization Agreement
NMP License and Commercialization Agreement
Upfront payment received	$ 1,000,000
Performance obligation	$ 1,000,000
Performance obligation period of recognition		6 years
Deferred revenue		$ 400,000	400,000
Milestone revenue recognized			$ 0
Period of time for termination notice to be given prior to the first commercial sale in Japan	90 days
Period of time for termination notice to be given after the first commercial sale in Japan	6 months
Period of time for termination notice to be given after Company receives regulatory approval in Japan but fails to launch the product	6 months
NMP | Achievement Of Regulatory Milestones | License And Commercialization Agreement
NMP License and Commercialization Agreement
Number of cancer indications requiring achievement of regulatory goals | item	5
NMP | Achievement Of Regulatory Milestones | Maximum | License And Commercialization Agreement
NMP License and Commercialization Agreement
Potential milestone payment	$ 4,500,000

Stockholders' Equity - Issuance

Stockholders' Equity - Issuances Related to the License Agreement (Details)	Mar. 02, 2018$ / sharesshares	Oct. 24, 2017shares	Sep. 29, 2017itemshares	Mar. 31, 2018USD ($)
Common Stock Offering [Abstract]
Issuance of common stock in connection with equity offering (in shares)	20,535,714
Share price | $ / shares	$ 4.20
Net proceeds from issuance of stock | $				$ 80,941,381
Underwriting discounts and commissions | $				5,200,000
Offering expenses | $				$ 100,000
Issuances Related to the License Agreement
Number of shares of common stock filed on registration statement per Registration Rights Agreement		6,000,000
License Agreement | ABX
Issuances Related to the License Agreement
Common stock issued per agreement			2,000,000
Number Of Warrants Issued Per Agreement | item			2
Aggregate number of common stock shares that may be purchased by exercise of warrants			4,000,000
Number of warrants exercised | item			1
Stock Issued During Period Shares Warrant Exercise			3,278,000
License Agreement | ABX | Maximum
Issuances Related to the License Agreement
Aggregate number of common stock shares that may be purchased by exercise of warrants			4,000,000

Stockholders' Equity - Stock Op

Stockholders' Equity - Stock Options assumptions (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value Assumptions
Expected volatility	102.03%	93.02%
Risk-free interest rate	2.65%	2.12%
Weighted-average expected life (in years)	6 years 4 months 24 days	6 years 3 months 18 days
Dividend yield	0.00%	0.00%
1997 And 2007 Plans | Service Based Options
Additional disclosures
Vesting period	4 years
1997 And 2007 Plans | Service Based Options | Service based vesting, first period
Additional disclosures
Vesting period	2 years
Shares that will vest (as a percentage)	0.50%
1997 And 2007 Plans | Performance Based Options
Additional disclosures
Vesting period	4 years
2010 Equity Incentive Plan
Stock-Based Compensation Plans
Shares authorized and reserved	13,296,563		11,850,563
2010 Equity Incentive Plan | Minimum
Additional disclosures
Vesting period	3 years
2010 Equity Incentive Plan | Maximum
Additional disclosures
Vesting period	4 years

Stockholders' Equity - Stock 33

Stockholders' Equity - Stock Option Activity (Details)	3 Months Ended
	Mar. 31, 2018USD ($)$ / sharesshares
Equity [Abstract]
Unrecognized compensation cost, net of forfeitures | $	$ 3,400,000
Weighted average period to recognize stock compensation expense	2 years
Options
Outstanding, Beginning Balance | shares	5,878,660
Granted during period | shares	688,192
Exercised during period | shares	(561,088)
Expired during period | shares	(8,993)
Outstanding, Ending Balance | shares	5,996,771
Weighted-Average Exercise Price
Outstanding, Beginning Balance | $ / shares	$ 5.93
Granted during period | $ / shares	3.07
Exercised during period | $ / shares	4.10
Expired during period | $ / shares	3.06
Outstanding, Ending Balance | $ / shares	$ 5.78
Additional disclosures
Options, Exercisable | shares	4,290,445
Weighted Average Exercise Price, Exercisable | $ / shares	$ 6.92
Weighted Average Remaining Contractual Term	6 years 2 months 5 days
Weighted Average Remaining Contractual Term exercisable at end of period	5 years 7 days
Aggregate Intrinsic Value | $	$ 22,125,418
Aggregate Intrinsic Value, exercisable at end of period | $	$ 11,551,954

Stockholders' Equity - Restrict

Stockholders' Equity - Restricted Stock Units (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)$ / sharesshares
Restricted Stock Units
Weighted average period to recognize stock compensation expense	2 years
RSUs
Restricted Stock Units
Number of shares of common stock to be paid upon vesting of RSU	1
Unrecognized compensation cost | $	$ 5.7
Weighted average period to recognize stock compensation expense	1 year 4 months 24 days
Restricted Stock Units
Outstanding at beginning of period	1,383,770
Granted during period	301,958
Vested during period	(161,147)
Outstanding at the end of the period	1,524,581
Weighted-Average Grant Date Fair Value
Outstanding beginning of period | $ / shares	$ 5.05
Granted during period | $ / shares	3.02
Vested during period | $ / shares	4.27
Outstanding end of period | $ / shares	$ 4.73
Minimum | 2010 Equity Incentive Plan
Restricted Stock Units
Vesting period	3 years
Minimum | RSUs
Restricted Stock Units
Vesting period	3 years
Maximum | 2010 Equity Incentive Plan
Restricted Stock Units
Vesting period	4 years
Maximum | RSUs
Restricted Stock Units
Vesting period	4 years

Stockholders' Equity - ESPP (De

Stockholders' Equity - ESPP (Details) - Shares to be purchased under the ESPP - shares	3 Months Ended
	Mar. 31, 2018	Jan. 01, 2018
Employee Stock Purchase Plan (Abstract)
Shares available for issuance under ESPP	769,542	769,542
Number of shares purchased under ESPP	0

Warrants (Details)

Warrants (Details) $ / shares in Units, $ in Millions	Sep. 29, 2017USD ($)item$ / sharesshares	Mar. 31, 2018itemshares
Class of Warrant or Right [Line Items]
Number of calendar days prior to warrant issue the average closing price of common stock used to determine warrant exercise price	30 days
Common Stock
Class of Warrant or Right [Line Items]
Warrant exercise price | $ / shares	$ 1.39
Warrant One
Class of Warrant or Right [Line Items]
Proceeds from Warrant Exercises | $	$ 4.6
Warrant Two
Class of Warrant or Right [Line Items]
Number of shares into which the remaining warrant could be converted		722,000
Expected term of warrants	10 years
Historic volatility used to value the warrants	91.10%
Interest rate assumption used to value the warrants	2.28%
Number of other warrants outstanding | item		0
License Agreement | ABX
Class of Warrant or Right [Line Items]
Number Of Warrants Issued Per Agreement | item	2
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	4,000,000
Stock Issued During Period Shares Warrant Exercise	3,278,000
License Agreement | Maximum | ABX
Class of Warrant or Right [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	4,000,000

Income Taxes (Details)

Income Taxes (Details)	Jan. 01, 2018	Dec. 31, 2017
Effect Of Tax Cuts And Jobs Act Of 2017 Accounting Incomplete Provisional [Abstract]
Corporate income tax rate	21.00%	35.00%

Restructuring Costs (Details)

Restructuring Costs (Details) - USD ($)	1 Months Ended	3 Months Ended
	Jun. 30, 2017	Mar. 31, 2018	Jun. 30, 2017
Restructuring Costs
Reduction in workforce (as a percent)	40.00%
Restructuring expense			$ 2,300,000
EC1456 Phase 1 Trial Termination Accrual
Restructuring Costs
Accrual balance		$ 106,900
Restructuring Reserve [Roll Forward]
Balance at beginning of period		(106,900)
Amounts paid during the period		(83,600)
Balance at end of period		$ (23,300)
General and Administrative Expense
Restructuring Costs
Employee termination benefits			100,000
Research and Development Expense.
Restructuring Costs
Employee termination benefits			900,000
Remaining EC1456 phase 1b trial expenses, including site close-out expenses			900,000
Other restructuring expenses			300,000
Fixed asset impairment			$ 100,000