Stemline Therapeutics (STML) 10-Q 8 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 08, 2018
Document and Entity Information
Entity Registrant Name	STEMLINE THERAPEUTICS INC
Entity Central Index Key	1,264,587
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		31,800,694
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3

Balance Sheets

Balance Sheets - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 11,677,741	$ 4,795,098
Short-term investments	66,856,499	46,924,612
Prepaid expenses and other current assets	1,996,235	469,067
Total current assets	80,530,475	52,188,777
Property and equipment, net	221,820	136,672
Long-term investments		14,468,414
Other assets	212,305	212,305
Total assets	80,964,600	67,006,168
Current liabilities:
Accounts payable and accrued expenses	17,202,090	19,742,087
Other current liabilities	133,170	96,826
Total current liabilities	17,335,260	19,838,913
Other liabilities	91,174	96,826
Total liabilities	17,426,434	19,935,739
Commitments and Contingencies (Note 14)
Stockholders' equity:
Preferred stock $0.0001 par value, 5,000,000 shares authorized, none issued and outstanding at September 30, 2018 and December 31, 2017
Common stock $0.0001 par value, 53,750,000 shares authorized at September 30, 2018 and December 31, 2017. 31,671,552 shares issued and outstanding at September 30, 2018 and 25,313,595 shares issued and outstanding at December 31, 2017	3,167	2,531
Additional paid-in capital	326,084,695	251,489,546
Accumulated other comprehensive loss	(96,546)	(145,958)
Accumulated deficit	(262,453,150)	(204,275,690)
Total stockholders' equity	63,538,166	47,070,429
Total liabilities and stockholders' equity	$ 80,964,600	$ 67,006,168

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	53,750,000	53,750,000
Common stock, shares issued	31,671,552	25,313,595
Common stock, shares outstanding	31,671,552	25,313,595

Statements of Operations

Statements of Operations - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income:
Grant income		$ 299,397	$ 500,000	$ 898,199
Operating expenses:
Research and development	$ 11,758,025	12,417,652	35,650,147	33,517,006
General and administrative	9,647,336	4,152,449	24,208,551	14,000,854
Total operating expenses	21,405,361	16,570,101	59,858,698	47,517,860
Loss from operations	(21,405,361)	(16,270,704)	(59,358,698)	(46,619,661)
Other Income		381		381
Other expense		(3,566)	(3,897)	(3,566)
Interest expense	(350)		(473)
Interest income	361,715	217,742	973,617	543,753
Net loss	$ (21,043,996)	$ (16,056,147)	$ (58,389,451)	$ (46,079,093)
Net loss per common share:
Basic and Diluted (in dollars per share)	$ (0.73)	$ (0.68)	$ (2.07)	$ (2.01)
Weighted-average shares outstanding:
Basic and Diluted (in shares)	29,018,507	23,464,505	28,253,750	22,901,883

Statements of Comprehensive Los

Statements of Comprehensive Loss - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statements of Comprehensive Loss
Net loss	$ (21,043,996)	$ (16,056,147)	$ (58,389,451)	$ (46,079,093)
Other comprehensive gain:
Unrealized gain on investments	26,427	30,207	45,515	9,112
Reclassification adjustment for loss on investments included in net loss		3,007	3,897	3,007
Other comprehensive gain	26,427	33,214	49,412	12,119
Comprehensive loss	$ (21,017,569)	$ (16,022,933)	$ (58,340,039)	$ (46,066,974)

Statement of Stockholders' Equi

Statement of Stockholders' Equity - 9 months ended Sep. 30, 2018 - USD ($)	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Total
Balance at Dec. 31, 2017	$ 2,531	$ 251,489,546	$ (145,958)	$ (204,275,690)	$ 47,070,429
Balance (in shares) at Dec. 31, 2017	25,313,595
Increase (Decrease) in Stockholders' Equity
Restricted stock grants	$ 150	(150)
Restricted stock grants (in shares)	1,496,126
Forfeiture of restricted stock grants	$ (6)	6
Forfeiture of restricted stock grants (in shares)	(55,495)
Stock-based compensation expense		8,682,492			8,682,492
Adoption of accounting standard update related to stock compensation accounting (ASU 2018-07)		(211,991)		211,991
Employee Stock Purchase Plan compensation expense		42,275			42,275
Issuance of common stock in connection with the ESPP	$ 2	142,918			142,920
Issuance of common stock in connection with the ESPP (in shares)	19,107
Issuance of common stock in connection with the exercise of stock options	$ 17	1,583,780			$ 1,583,797
Issuance of common stock in connection with the exercise of stock options (in shares)	169,810				169,810
Issuance of common stock in connection with the exercise of warrants	$ 3	352,525			$ 352,528
Issuance of common stock in connection with the exercise of warrants (in shares)	30,830
Issuance of common stock in connection with follow-on public offering, net	$ 470	64,003,294			64,003,764
Issuance of common stock in connection with follow-on public offering, net (in shares)	4,697,579
Net loss				(58,389,451)	(58,389,451)
Other comprehensive income			49,412		49,412
Balance at Sep. 30, 2018	$ 3,167	$ 326,084,695	$ (96,546)	$ (262,453,150)	$ 63,538,166
Balance (in shares) at Sep. 30, 2018	31,671,552

Statements of Cash Flows

Statements of Cash Flows - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities
Net loss	$ (58,389,451)	$ (46,079,093)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	38,639	2,856
Stock-based compensation expense	8,682,492	6,178,079
Employee Stock Purchase Plan compensation expense	42,275	38,897
Amortization of premium paid on marketable securities	(55,505)	119,355
Net gain on sale of marketable securities	3,897	3,007
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,527,168)	(307,609)
Accounts payable and accrued expenses	(2,539,997)	5,043,713
Deferred grant income		(898,199)
Other current liabilities	28,433	25,727
Other liabilities	(24,203)	(21,167)
Net cash used in operating activities	(53,740,588)	(35,894,434)
Cash flows from investing activities
Purchase of furniture and fixtures	(94,258)	(86,191)
Purchase of marketable securities	(57,750,123)	(55,396,963)
Sale and maturities of marketable securities	52,387,670	42,955,816
Net cash used in investing activities	(5,456,711)	(12,527,338)
Cash flows from financing activities
Principal payments on finance lease liabilities	(3,067)
Proceeds from issuance of common stock from follow-on public offerings, net	64,003,764	48,242,214
Proceeds from issuance of common stock from ESPP	142,920	121,671
Proceeds from exercise of stock options	1,583,797	7,179
Proceeds from exercise of warrants	352,528
Net cash provided by financing activities	66,079,942	48,371,064
Net increase (decrease) in cash and cash equivalents	6,882,643	(50,708)
Cash and cash equivalents at beginning of period	4,795,098	10,316,064
Cash and cash equivalents at end of period	$ 11,677,741	$ 10,265,356

Statements of Cash Flows (Paren

Statements of Cash Flows (Parenthetical)	9 Months Ended
	Sep. 30, 2018USD ($)
Statements of Cash Flows
Capital lease obligation incurred	$ 29,529

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Organization and Basis of Presentation
Organization and Basis of Presentation	1. Organization and Basis of Presentation Organization Stemline Therapeutics, Inc. (the “Company”) is a clinical-stage biopharmaceutical company focused on discovering, acquiring, developing and potentially commercializing novel oncology therapeutics. The Company’s activities to date have primarily consisted of advancing its clinical stage programs and regulatory interactions, preparing for a potential commercial launch, expanding and strengthening its intellectual property portfolio, undertaking research and development activities, identifying and acquiring additional product and technology rights and raising capital. The Company was incorporated in Delaware on August 8, 2003 and has its principal office in New York, New York. The Company has incurred losses from operations since inception of $274.1 million. Since its inception, most of its resources have been dedicated to the discovery, acquisition, preclinical and clinical development of its product candidates and preparation for a potential commercial launch of ELZONRIS™ (tagraxofusp; SL-401). In particular, it has expended, and will continue to expend, substantial resources for the foreseeable future on potential commercialization of any products approved for marketing, continued development of its product candidate pipeline, as well as on drug discovery and acquisition efforts. The Company will also incur losses as it prepares for a potential commercial launch of ELZONRIS. These expenditures include costs associated with general and administrative costs, facilities costs, research and development, acquiring new technologies, manufacturing product candidates, conducting preclinical experiments and clinical trials, and obtaining regulatory approvals, as well as commercializing any products approved for sale. The Company anticipates incurring additional losses until such time, if ever, that it can generate significant sales of its products currently in development. The Company expects its research and development expenses to trend higher in connection with its ongoing and planned clinical trials and related manufacturing efforts for its clinical stage candidates and development of its other pre-clinical product candidates, platform technologies and in-licensing activities. The Company also anticipates that its general and administrative expenses will be higher in future periods due to the build out of a commercial infrastructure and regulatory compliance systems to support potential commercialization of ELZONRIS if an FDA or foreign equivalent health authority approval for marketing is obtained. As a result, the Company expects to continue to incur significant and increasing operating losses for the foreseeable future. If adequate funds are not available to the Company on a timely basis, or at all, the Company may be required to terminate or delay clinical trials or other development activities for its clinical stage candidates, for one or more indications, or delay its establishment of sales and marketing capabilities or other activities that may be necessary to commercialize any products approved for sale. Basis of Presentation The accompanying unaudited financial statements have been prepared in accordance with the United States generally accepted accounting principles (“GAAP”) and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all information and footnotes required by GAAP for complete financial statements. In the opinion of management, the accompanying financial statements include all adjustments (including normal recurring adjustments) considered necessary for fair presentation of the Company’s financial position, results of operations and cash flows for the periods presented. Operating results for the current interim period are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2018 or any future periods. This Form 10-Q should be read in conjunction with the audited financial statements and accompanying notes in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 (“2017 Form 10-K”). The Company believes that its existing cash, cash equivalents, short-term investments and long-term investments will be sufficient to cover its cash flow requirements for at least the next two years, assuming an FDA approval is granted for marketing of ELZONRIS by the target action PDUFA date of February 21, 2019. Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles in the U.S. ("U.S. GAAP") requires management to make estimates and assumptions that affect the reported financial position at the date of the financial statements and the reported results of operations during the reporting period. Such estimates and assumptions affect the reported amounts of assets, liabilities, income and expenses and disclosure of contingent assets and liabilities in the financial statements and accompanying notes. Actual results could differ from those estimates. Reclassifications Certain reclassifications have been made to footnote 7 “Accounts Payable and Accrued Expenses” for the period ended December 31, 2017 to conform to the presentation under the period ended September 31, 2018. These reclassifications to adjust prior period presentation had no impact on previously reported accrued expenses.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies The Company’s significant accounting policies are described in Note 2 of the Notes to the Financial Statements included in the 2017 Form 10-K. There have been no changes to those policies. Recently Issued Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”), issued a comprehensive new revenue recognition Accounting Standards Update, Revenue From Contracts With Customers (Topic 606) (ASU 2014-09). ASU 2014-09 provides guidance to clarify the principles for recognizing income. This guidance includes the required steps to achieve the core principle that an entity should recognize income 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. This guidance is effective for fiscal years and interim periods beginning after December 15, 2017. Early adoption is permitted for fiscal years and interim periods beginning after December 15, 2016. The Company adopted this guidance on January 1, 2018 using the full retrospective method. The accounting standard had no impact on the financial position, results of operations or cash flows since the Company has no contracts with customers. Any future contracts with customers will be accounted for under the new guidance effective January 1, 2018. As noted below in Note 11 to the Company's Financial Statements, the Company has received grant income from The Leukemia and Lymphoma Society (“LLS”) to fund the Company's development program related to the Company's preclinical and clinical product development activities. The Company has determined that LLS is not a customer as defined by Topic 606. The Company recognizes grant income when there is reasonable assurance of compliance with the conditions of the grant and reasonable assurance that the grant income will be received based on the Company's best estimates of work performed and qualifying costs incurred. In January 2016, the FASB issued a new Accounting Standards Update, Recognition and Measurement of Financial Assets and Financial Liabilities (ASU 2016-01). ASU 2016-01 amends the guidance in U.S. GAAP on the classification and measurement of financial instruments. Although the ASU retains many current requirements, it significantly revises an entity’s accounting related to (1) the classification and measurement of investments in equity securities and (2) the presentation of certain fair value changes for financial liabilities measured at fair value. The ASU also amends certain disclosure requirements associated with the fair value of financial instruments. The new standard is effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2017, with early adoption permitted for certain changes. The Company adopted this guidance on January 1, 2018 and it had no impact on the financial position, results of operations or cash flows. In February 2016, the FASB issued a new Accounting Standards Update , Leases (ASU 2016-02). ASU 2016-02 is aimed at making leasing activities more transparent and comparable and requires most leases be recognized by lessees on the Balance Sheets as a right-of-use asset and corresponding lease liability, regardless of whether they are classified as finance or operating leases. The new standard is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period, with early adoption permitted. The Company is currently evaluating the impact of the new pronouncement on the Company’s financial statements and related disclosures. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230), Classification of Certain Cash Receipts and Cash Payments . ASU 2016-15 clarifies how entities should classify certain cash receipts and cash payments on the Statement of Cash Flows and amends certain disclosure requirements of ASC 230. The guidance will generally be applied retrospectively and is effective for public business entities for fiscal years beginning after December 15, 2017, and interim periods within those years. For all other entities, it is effective for fiscal years beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019. Early adoption is permitted, including adoption in an interim period. If an entity early adopts the guidance in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. An entity that elects early adoption must adopt all of the guidance in the same period. The Company adopted this guidance on January 1, 2018 and it had no impact to the Statement of Cash Flows. In May 2017, the FASB issued ASU No. 2017-09, Compensation - Stock Compensation (Topic 718), Scope of Modification Accounting . ASU 2017-09 provides guidance on the types of changes to the terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting. ASU 2017-09 is applied prospectively to awards modified on or after the effective date. The Company adopted ASU 2017-09 on January 1, 2018. The adoption of this standard did not have a material impact to the Company’s Balance Sheets, Statement of Operations, or Statement of Cash Flows. On December 22, 2017, the Tax Cuts and Jobs Act (the “TCJ Act” or the “Tax Act”) was enacted into law. The TCJ Act provides for significant changes to the U.S. Internal Revenue Code of 1986, as amended (the “Code”), that impact corporate taxation requirements, such as the reduction of the federal tax rate for corporations from 35% to 21% and changes or limitations to certain tax deductions. The reduction in the corporate tax rate under the TCJ Act will also require a one-time revaluation of certain tax-related assets to reflect their value at the lower corporate tax rate of 21%. As such, the Company currently calculates a reduction in the value of these assets of approximately $25.0 million, which is fully offset by a valuation allowance and has no impact on the income tax provision. The company is still evaluating the full impact of the TCJ Act but due to a full valuation against deferred taxes, the company estimates no impact to the income tax provision. On June 20, 2018, the FASB issued ASU No. 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting , which expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. Entities should apply the requirements of Topic 718 to nonemployee awards except for specific guidance on inputs to an option pricing model and the period of time equity awards vest and the pattern of cost recognition over that period. ASU No. 2018-07 is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted and the Company adopted ASU No. 2018-07 on April 1, 2018. The Company early adopted ASU No. 2018-07 on April 1, 2018 and the net impact relating to the adoption was a $0.2 million decrease to accumulated deficit for the impact prior to April 1, 2018. In addition, the Company has elected to account for forfeitures of nonemployee awards as they occur. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements. The ASU allows entities to not recast comparative periods in transition to ASC 842 and instead report the comparative periods presented in the period of adoption under ASC 840. The ASU also includes a practical expedient for lessors to not separate the lease and non-lease components of a contract. The amendments in this ASU are effective in the same time-frame as ASU 2016-02 as discussed above. The Company is incorporating this ASU into its assessment and adoption of ASU 2016-02. In August 2018, the FASB issued ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement”, which adds disclosure requirements to Topic 820 for the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. This ASU is effective for interim and annual reporting periods beginning after December 15, 2019. The adoption of ASU 2018-13 is not expected to have an impact on the Company's financial statements. In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification, amending certain disclosure requirements that were redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expanded the disclosure requirements on the analysis of stockholders' equity for interim financial statements. Under the amendments, an analysis of changes in each caption of stockholders' equity presented in the balance sheets must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed. As such, the Company adopted these SEC amendments on November 5, 2018 and will present the analysis of changes in stockholders’ equity in its interim financial statements in its March 31, 2019 Form 10-Q. The Company does not anticipate that the adoption of these SEC amendments will have a material effect on the Company’s financial position, results of operations, cash flows or shareholders’ equity.

Liquidity and Capital Resources

Liquidity and Capital Resources	9 Months Ended
	Sep. 30, 2018
Liquidity and Capital Resources
Liquidity and Capital Resources	3. Liquidity and Capital Resources As of September 30, 2018, the Company has approximately $78.5 million in cash, cash equivalents and short and long-term investment securities. The Company primarily invests in highly liquid cash equivalents, short-term investments and long-term investments in U.S. Treasury and Agency securities and related money market funds and FDIC-insured bank certificates of deposit, with the balance in commercial bank operating accounts.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	9 Months Ended
	Sep. 30, 2018
Prepaid Expenses and Other Current Assets
Prepaid Expenses and Other Current Assets	4. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following at September 30, 2018 and December 31, 2017: September 30, December 31, 2018 2017 Prepaid third party vendor costs $ 877,886 $ 131,286 Deferred registration fees — 143,924 Prepaid insurance 250,542 44,065 Deposit 69,660 — Other receivable 798,147 149,792 Total $ 1,996,235 $ 469,067

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2018
Property and Equipment, Net
Property and Equipment, Net	5. Property and Equipment, Net Property and equipment, net, consist of the following at September 30, 2018 and December 31, 2017: September 30, December 31, 2018 2017 Office furniture and fixtures $ 519,675 $ 519,675 Leasehold improvements 82,694 82,694 Capital lease equipment 29,529 — Manufacturing equipment 107,258 13,000 Property and equipment 739,156 615,369 Less accumulated depreciation (517,336) (478,697) Property and equipment, net $ 221,820 $ 136,672 Depreciation expense was $38,639 and $2,856 for the nine-month periods ended September 30, 2018 and 2017, respectively. Depreciation expense was $14,575 and $952 for the three-month periods ended September 30, 2018 and 2017, respectively.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Measurements
Fair Value Measurements	6. Fair Value Measurements Fair value is defined as the exchange price that would be received for an asset or amount paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Assets and liabilities that are measured at fair value are reported using a three-level fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and minimizes the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows: Level 1 — Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2 — Inputs other than quoted prices in active markets that are observable for the asset or liability, either directly or indirectly. Level 3 — Inputs that are unobservable for the asset or liability. The following fair value hierarchy table presents information about each major category of the Company’s financial assets and liability measured at fair value on a recurring basis as of September 30, 2018 and December 31, 2017: September 30, 2018 Quoted Prices in Active Significant Markets for Other Significant Balance Identical Observable Unobservable at Assets Inputs Inputs September 30, (Level 1) (Level 2) (Level 3) 2018 Assets: Fixed-income treasury portfolio $ 43,051,836 $ — $ — $ 43,051,836 Certificate of Deposits — 23,804,663 — 23,804,663 Cash and cash equivalents 11,677,741 — — 11,677,741 Total assets at fair value $ 54,729,577 $ 23,804,663 $ — $ 78,534,240 December 31, 2017 Quoted Prices in Active Significant Markets for Other Significant Balance Identical Observable Unobservable at Assets Inputs Inputs December 31, (Level 1) (Level 2) (Level 3) 2017 Assets: Fixed-income treasury portfolio $ 40,160,213 $ — $ — $ 40,160,213 Certificate of Deposits — 21,232,813 — 21,232,813 Cash and cash equivalents 4,795,098 — — 4,795,098 Total assets at fair value $ 44,955,311 $ 21,232,813 $ — $ 66,188,124 The following is a summary of cash equivalents and available-for-sale investments held by the Company at September 30, 2018 and December 31, 2017: September 30, 2018 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains* Losses* Value Cash: Cash from operating accounts $ 7,604,252 $ — $ — $ 7,604,252 Cash equivalents: Money market funds 4,073,489 — — 4,073,489 Total cash and cash equivalents 11,677,741 — — 11,677,741 Short-term investments: Fixed-income treasury portfolio: Fannie Mae 6,655,875 — (6,467) 6,649,408 Federal home loan bank 11,312,471 — (23,642) 11,288,829 Freddie Mac 5,263,336 — (15,376) 5,247,960 U.S. Treasury Securities 19,891,015 — (25,376) 19,865,639 Certificate of Deposits 23,805,052 — (389) 23,804,663 Total short-term investments 66,927,749 — (71,250) 66,856,499 Total $ 78,605,490 $ — $ (71,250) $ 78,534,240 December 31, 2017 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains* Losses* Value Cash: Cash from operating accounts $ 3,088,659 $ — $ — $ 3,088,659 Cash equivalents: Money market funds 1,706,439 — — 1,706,439 Total cash and cash equivalents $ 4,795,098 — — $ 4,795,098 Short-term investments: Fixed-income treasury portfolio: Fannie Mae 13,631,041 — (31,396) 13,599,645 Federal farm credit bank 1,249,823 — (1,869) 1,247,954 Federal home loan bank 5,923,497 — (14,197) 5,909,300 Freddie Mac 5,409,227 — (19,182) 5,390,045 U.S. Treasury Securities 6,282,231 — (12,578) 6,269,653 Others 1,019,302 — (612) 1,018,690 Certificate of Deposits 13,489,241 84 — 13,489,325 Total short-term investments 47,004,362 84 (79,834) 46,924,612 Long-term investments: Fixed-income treasury portfolio: Federal home loan bank 2,753,337 — (15,529) 2,737,808 Freddie Mac 2,509,471 — (13,635) 2,495,836 U.S. Treasury Securities 1,503,030 — (11,748) 1,491,282 Certificate of Deposits 7,743,488 — — 7,743,488 Total long-term investments 14,509,326 — (40,912) 14,468,414 Total $ 66,308,786 $ 84 $ (120,746) $ 66,188,124 *The gross unrealized gains and losses captured in this footnote is before tax. At September 30, 2018 and December 31, 2017, the remaining contractual maturities of available-for-sale investments classified as current on the Balance Sheets were less than 12 months, and the remaining contractual maturities of available-for-sale investments classified as long-term were less than two years. There were no available-for-sale securities in a continuous unrealized loss position for greater than twelve months at September 30, 2018 and December 31, 2017. The Company has the ability to hold such securities with an unrealized loss until its forecasted recovery. The Company determined that there was no material change in the credit risk of the above investments. As a result, the Company determined it did not hold any investments with an other-than-temporary impairment as of September 30, 2018. Fair Value of Financial Instruments The Company’s financial instruments consist principally of cash and cash equivalents, investments, other current assets, accounts payable and accrued expenses. Cash and cash equivalents, short-term investments and long-term investments are carried at fair value (see above). Financial instruments including other current assets, accounts payable and accrued expenses are carried at cost, which approximate fair value given their short-term nature.

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	9 Months Ended
	Sep. 30, 2018
Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Expenses	7. Accounts Payable and Accrued Expenses Accounts payable and accrued expenses consist of the following at September 30, 2018 and December 31, 2017: September 30, December 31, 2018 2017 Accrued research and development costs $ 9,188,824 $ 14,805,432 Accrued sales and marketing costs 3,187,821 668,512 Accrued compensation 2,356,275 2,940,039 Accrued general and administrative costs 1,555,056 511,140 Accrued legal 914,114 816,964 Total accounts payable and accrued expenses $ 17,202,090 $ 19,742,087

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2018
Common Stock
Common Stock	8. Common Stock For the nine-month period ended September 30, 2018, the Company received net proceeds of $8.3 million from an At-the-Market (ATM) offering, selling 442,579 shares at an average price of $19.24 per share. The Company did not sell any shares of stock from the ATM during the three-month period ending September 30, 2018. On January 26, 2018, the Company completed a fourth follow-on public offering, selling 3,700,000 shares at an offering price of $14 per share. Additionally, the underwriters exercised, in full, their over-allotment option to purchase an additional 555,000 shares at an offering price of $14 per share. Aggregate gross proceeds from the follow-on public offering, including the exercise of the over-allotment option, were $59.6 million, and net proceeds received after underwriting fees and offering expenses were approximately $55.7 million. In January 2013, the Company issued warrants to purchase up to 99,529 shares of the Company’s common stock. The warrants became exercisable during January 2014. The warrants were exercisable for cash or on a cashless basis at a price per share equal to $15.00. The term of the warrants was five years and they were set to expire on January 28, 2018. During January 2018, the Company’s warrant holders elected to exercise warrants to purchase 99,529 shares of the Company’s common stock, whereby the Company received approximately $0.4 million in connection with this exercise. A portion of the transaction was processed via a cashless exercise. As of September 30, 2018 and December 31, 2017, the Company was authorized to issue 53,750,000 shares of common stock. Dividends on common stock will be paid when, and if, declared by the board of directors. Each holder of common stock is entitled to vote on all matters and is entitled to one vote for each share held. The Company will, at all times, reserve and keep available, out of its authorized but unissued shares of common stock, sufficient shares to affect the conversion of shares from the exercise of stock options.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2018
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Loss	9. Accumulated Other Comprehensive Loss The changes in accumulated balances for each component of other comprehensive loss are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Balance at beginning of period $ (122,973) $ (120,897) $ (145,958) $ (99,802) Other comprehensive income (loss) before reclassification 26,427 30,207 45,515 9,112 Amounts reclassified from accumulated other comprehensive income (loss) — 3,007 3,897 3,007 Total other comprehensive income 26,427 33,214 49,412 12,119 Balance at end of period $ (96,546) $ (87,683) $ (96,546) $ (87,683) *Amounts reclassified affect other income in the Statements of Operations.

Net (Loss) Income Per Common Sh

Net (Loss) Income Per Common Share	9 Months Ended
	Sep. 30, 2018
Net (Loss) Income Per Common Share
Net (Loss) Income Per Common Share	10. Net (Loss) Income Per Common Share The Company accounts for and discloses net loss per share using the treasury stock method. Net loss per common share, or basic loss per share, is computed by dividing net loss by the weighted-average number of common shares outstanding. Since the Company is in a net loss for all periods presented, diluted net loss per share is not presented since the common stock equivalents would have an anti-dilutive effect on the per share calculation. The following table sets forth the computation of basic and diluted net loss per share for the periods indicated: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Basic and diluted net loss per common share calculation: Net loss $ (21,043,996) $ (16,056,147) $ (58,389,451) $ (46,079,093) Basic and diluted weighted-average common shares 29,018,507 23,464,505 28,253,750 22,901,883 Basic and diluted net loss per share $ (0.73) $ (0.68) $ (2.07) $ (2.01) The difference between basic and diluted weighted-average common shares generally results from the assumption that dilutive stock options outstanding were exercised, dilutive restricted stock has vested, and outstanding warrants are issued. For the nine-month periods ended September 30, 2018 and 2017, the Company reported a loss from operations and therefore, all potentially dilutive stock options, restricted stock, and outstanding warrants as of such date were excluded from the computation of diluted net loss per share as their effect would have been anti-dilutive. The total shares of stock options, restricted stock, and outstanding warrants that could potentially dilute earnings per share in the future, but which were not included in the calculation of diluted net loss per share because their affect would have been anti-dilutive were as follows: Nine Months Ended September 30, 2018 2017 Restricted stock 2,631,934 1,796,749 Options outstanding 3,191,018 3,200,211 Warrants — 99,529 Total 5,822,952 5,096,489

Grant Income

Grant Income	9 Months Ended
	Sep. 30, 2018
Grant Income
Grant Income	11. Grant Income In October 2013, the Company entered into a contract relating to the Therapy Acceleration Program (“the TAP Agreement”) with LLS. LLS is a national voluntary health agency which, among other activities, encourages and sponsors research relating to blood cancers to develop therapies to cure or mitigate these diseases. To further its mission, LLS provides research funding to entities that can demonstrate after LLS’s review process that their proposed research projects have scientific promise to advance LLS’s effort to find treatments and cures for blood cancers and their complications. Pursuant to the TAP Agreement, LLS agreed to provide funding to the Company not to exceed $3.5 million to fund the Company’s development program related to the Company’s preclinical and clinical product development activities. Through September 30, 2018, the Company has received the full $3.5 million based on milestones achieved. The Company has recognized approximately $0.5 million and $0.9 million of income related to the LLS grant for the nine-month periods ended September 30, 2018 and 2017, respectively, which reflects income recognized on a straight-line basis based on the Company’s best estimates of work performed and qualifying costs incurred. The TAP Agreement terminates when there are no longer any payment obligations for either LLS or Stemline.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Taxes
Income Taxes	12. Income Taxes The Company did not record any other income tax provisions or benefits relating to its net operating losses for the nine-month periods ended September 30, 2018 and September 30, 2017, respectively, due to the fact that the Company cannot benefit from its net operating losses or other deferred tax assets. The Company does not currently have the ability to carry back losses to previous years to recover taxes paid and future utilization of these losses is uncertain. The Company files income tax returns in the United States and in the State of New York. The Company’s 2015 tax years are currently being audited by the Internal Revenue Service and there are no ongoing audits in state taxing jurisdictions. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and their basis for income tax purposes and the tax effects of net operating loss and tax credit carryforwards. Valuation allowances reduce deferred tax assets to the amounts that are more likely than not to be realized. As of September 30, 2018, the Company has recorded additional deferred tax assets which are fully offset by a valuation allowance. Realization of the deferred tax assets is dependent on generating sufficient taxable income in the future. At present, the likelihood of the Company being able to fully utilize its deferred income tax benefits against future income is uncertain. The SEC staff issued SAB 118, which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Act for which the accounting under ASC 740 is complete. To the extent that a company's accounting for certain income tax effects of the Tax Act is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Act. As noted in the 2017 Form 10-K, the Company was able to reasonably estimate certain tax effects and, therefore, recorded provisional adjustments associated with the impact of tax reform. The Company has not made any additional measurement-period adjustments related to tax reform during the quarter ended September 30, 2018. However, the Company is continuing to gather additional information to complete its accounting for these items and expects to complete its accounting within the prescribed measurement period.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2018
Stock-Based Compensation
Stock-Based Compensation	13. Stock-Based Compensation The Company’s 2016 Stock Equity Incentive Plan (the “2016 Plan”) was adopted by the board of directors and approved by the stockholders in May 2016. The 2016 Plan authorizes the Company to grant up to 1,812,932 shares of common stock to eligible employees, directors, and non-employee consultants and advisors to the Company. During June 2017, an amendment was approved by the stockholders to increase the authorized shares under the 2016 plan by 1,200,000 shares. An amendment was approved by the stockholders at the 2018 Annual Meeting of Stockholders on June 21, 2018, to increase the authorized shares under the 2016 plan by 2,900,000 shares. Under the provisions of the 2016 Plan, no option will have a term in excess of 10 years. The Company’s 2012 Stock Equity Incentive Plan (the “2012 Plan”), which was adopted by the board of directors and approved by the stockholders in July 2012, became effective immediately prior to the closing of the Company’s initial public offering. In addition, the Company’s 2004 Stock Option and Grant Plan (the “2004 Plan”) was terminated effective immediately prior to the closing of the Company’s initial public offering. The 2012 Plan authorized the Company to grant up to 1,663,727 shares of common stock to eligible employees, directors, and non-employee consultants and advisors to the Company. Under the provisions of the 2012 Plan, no option will have a term in excess of 10 years. With the adoption of the 2016 plan, all authorized but un-issued shares, totaling 12,932, under the 2012 plan were converted to the 2016 plan. All future awards will be granted out of the 2016 plan. As of September 30, 2018, there were 2,358,480 shares of common stock available for future grants under the 2016 Plan. Total compensation cost that has been charged against operations related to the above plans was approximately $8.7 million and $6.2 million for the nine-month periods ended September 30, 2018 and 2017, respectively. As a result of the valuation allowance against the Company’s deferred tax assets, there was no net adjustment to retained earnings for the change in accounting for unrecognized windfall tax benefits. The following table summarizes stock-based compensation related to the above plans by expense category for the three-month and nine-month periods ended September 30, 2018 and 2017, respectively: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Research and development $ 1,334,967 $ 995,488 $ 3,521,610 $ 2,622,790 General and administrative 1,735,457 1,253,499 5,160,882 3,555,289 Total $ 3,070,424 $ 2,248,987 $ 8,682,492 $ 6,178,079 Stock Options The Company grants stock options to employees, directors and non-employee consultants, with exercise prices equal to the closing price of the underlying shares of the Company’s common stock on the date that the options are granted. Options granted have a term of 10 years from the grant date. Options granted to employees generally vest over a four-year period from the date of grant or if vesting based on market condition, awards vest based on the derived service period which is the estimated period of time that would be required to satisfy the market condition. Options granted to directors vest in equal yearly installments over a three-year period from the date of grant. Options to directors are granted on an annual basis and represent compensation for services performed on the Board of Directors. Compensation cost for stock options granted to employees and directors is charged against operations using the straight-line attribution method between the grant date for the option and each vesting date. The Company estimates the fair value of stock options on the grant date by applying the Black-Scholes option pricing valuation model. The application of this valuation model involves assumptions that are highly subjective, judgmental and sensitive in the determination of compensation cost. The weighted-average key assumptions used in determining the fair value of options granted for the three-month and nine-month periods ended September 30, 2018 and 2017, respectively are as follows: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Weighted-average volatility 75.35 % 75.36 % 76.90 % 75.76 % Weighted-average risk-free interest rate 2.86 % 1.98 % 2.78 % 1.92 % Weighted-average expected term in years 6.26 6.25 6.26 6.07 Dividend yield % % % % Due to the lack of trading history, the Company’s computation of stock-price volatility is based on the volatility rates of comparable publicly held companies over a period equal to the estimated useful life of the options granted by the Company. The Company’s computation of expected life was determined using the “simplified” method which is the midpoint between the vesting date and the end of the contractual term. The Company believes that it does not have sufficient reliable exercise data in order to justify the use of a method other than the “simplified” method of estimating the expected exercise term of employee stock option grants. The Company has paid no dividends to stockholders. The risk-free interest rate is based on the zero-coupon U.S. Treasury yield at the date of grant for a term equivalent to the expected term of the option. For the nine-month period ended September 30, 2018, the Company issued 169,810 shares, of the Company’s common stock upon the exercise of outstanding stock options and received proceeds of approximately $1.6 million. As of September 30, 2018, there was approximately $5.5 million of unrecognized compensation cost related to unamortized stock option compensation which is expected to be recognized over a remaining weighted-average period of approximately 1.77 years. The following table summarizes the activity related to the Company’s stock options for the nine months ended September 30, 2018: Weighted- Average Weighted- Remaining Aggregate Average Contractual Intrinsic Options Exercise Price Life Value Outstanding at December 31, 2017 3,174,964 $ 8.74 Options granted 275,000 16.40 Options exercised (169,810) 9.33 Options forfeited (89,136) 17.14 Outstanding at September 30, 2018 3,191,018 $ 9.13 5.96 $ 26,021,455 Options exercisable at September 30, 2018 2,216,605 $ 9.02 5.05 $ 18,841,644 The aggregate intrinsic value in the previous table reflects the total pretax intrinsic value (the difference between the Company’s closing stock price on the last trading day of the quarter ended September 30, 2018 and the exercise price of the options, multiplied by the number of in-the-money stock options) that would have been received by the option holders had all option holders exercised their options on September 30, 2018. The intrinsic value of the Company’s stock options changes based on the closing price of the Company’s common stock. Restricted Stock The Company grants restricted stock to its employees, directors, and non-employee consultants. Restricted stock is recorded as deferred compensation and charged against income on a straight-line basis over the vesting period, which ranges from immediate to four years in duration. If vesting of the award is based on a performance or market condition, awards vest based on the derived service period which is the estimated period of time that would be required to satisfy the performance or market condition. Restricted stock awards to directors vest in equal installments over a three-year period from the grant date. Compensation cost for restricted stock is based on the award’s grant date fair value, which is the closing market price of the Company’s common stock on the grant date, multiplied by the number of shares awarded. The following table summarizes the activity related to the Company’s restricted stock for the nine months ended September 30, 2018: Weighted- Average Grant Date Fair Value Number of Shares Per Share Outstanding at December 31, 2017 1,724,837 $ 7.83 Shares granted 1,496,126 16.83 Shares vested (533,534) 8.42 Shares forfeited (55,495) 11.52 Outstanding at September 30, 2018 2,631,934 $ 12.75 For the nine-month period ended September 30, 2018, the Company granted 1,496,126 shares of restricted stock, at a weighted-average grant date fair value of $16.83 per share amounting to approximately $25.2 million in total aggregate fair value. As of September 30, 2018, 2,631,934 shares remained unvested and there was approximately $28.5 million of unrecognized compensation cost related to restricted stock which is expected to be recognized over a remaining weighted-average period of approximately 1.98 years. The total fair value of restricted stock vested during the nine-month periods ended September 30, 2018 and 2017 was approximately $4.5 million and $3.0 million, respectively. Awards Granted to Non-Employee Consultants The Company grants stock options, restricted stock, and unrestricted stock to non-employee consultants. On June 20, 2018, the FASB issued ASU No. 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting , which expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The Company early adopted ASU No. 2018-07 on April 1, 2018 and the net impact relating to the adoption was a $0.2 million decrease to accumulated deficit for the impact prior to April 1, 2018 . Total compensation cost charged against operations related to stock-based awards granted to non-employee consultants was approximately $1.5 million and $0.5 million for the nine-month periods ended September 30, 2018 and 2017, respectively. Employee Stock Purchase Plan In September 2015, the Company adopted its 2015 Employee Stock Purchase Plan (the “2015 ESPP”). The 2015 ESPP is qualified as an employee stock purchase plan under Section 423 of the Internal Revenue Code of 1986, as amended (the “IRC”). Under the 2015 ESPP, the Company will grant rights to purchase shares of common stock under the 2015 ESPP (“Rights”) at prices not less than 85% of the lesser of (i) the fair value of the shares on the date of grant of such Rights or (ii) the fair value of the shares on the date such Rights are exercised. Therefore, the 2015 ESPP is considered compensatory under FASB ASC 718 since, along with other factors, it includes a purchase discount of greater than 5%. The Company recorded approximately $42,275 and $38,897 of compensation expense for the nine months ended September 30, 2018 and 2017, respectively, related to participation in the 2015 ESPP.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies
Commitments and Contingencies	14. Commitments and Contingencies The Company has entered into research and development agreements with third-parties for the development of oncology products and technologies. According to these agreements, the Company typically funds the development of such assets and potentially makes development-based milestone, royalties and sales-based milestone should the product candidates be approved for marketing. The timing and the amounts of milestone and royalty payments in the future are not certain. The Company has also entered into license agreements, including ones with licenses to certain intellectual property rights, in the field of oncology and other indications. The Company is generally required to make upfront payments as well as other payments upon successful completion of preclinical, clinical, regulatory or sales milestones, should such milestones occur. In addition, these agreements generally would require the Company to pay royalties on sales of the products arising from these agreements, should a product candidate under the license agreement receive regulatory approval. These agreements generally permit the Company to terminate the agreement with no significant continuing obligation. Under the Company’s research and development and/or license agreements, if the Company were to achieve certain milestones, primarily late stage clinical trial events, marketing approval, and sales, the Company could be required to pay up to a total of $217.1 million in future periods. As of September 30, 2018, the Company has paid or accrued $7.0 million in payments pursuant to such agreements. If a product candidate under such agreements were to receive marketing approval, royalty payments, largely single digit, are payable on commercial sales of certain products. The Company has committed to make potential future milestone and royalty payments to third-parties as part of its research and development and licensing agreements. Payments generally become due and payable only upon the achievement of certain developmental, regulatory and/or commercial milestones. Because the achievement of these milestones is neither guaranteed nor reasonably estimable, the Company has not recorded a liability on its Balance Sheets for any such contingencies. Contractual Agreements In February 2013, the Company entered into a bioprocessing services agreement with a vendor for approximately $2.9 million if all services are performed under the contract. As of December 31, 2014, the contract services were performed on the initial work order and had been paid by the Company. During 2013 through 2018, the Company entered into new work order agreements with this vendor totaling approximately $28.9 million, with services to be rendered on these agreements through 2018. From inception through September 30, 2018, the Company has received and paid for services relating to these agreements in the amount of approximately $24.8 million. The Company has agreements in place with contract research organizations, or CROs, in connection with its clinical programs. The Company’s total expenditures in the future would be approximately $4.4 million assuming the successful advancement of its programs. Therapy Acceleration Program Agreement with The Leukemia and Lymphoma Society In October 2013, the Company entered into a contract relating to the TAP Agreement with the LLS. The LLS is a national voluntary health agency which, among other activities, encourages and sponsors research relating to blood cancers to develop therapies to cure or mitigate these diseases. To further its mission, LLS provides research funding to entities that can demonstrate after LLS’s review process that their proposed research projects have scientific promise to advance LLS’s effort to find treatments and cures for blood cancers and their complications. Pursuant to the TAP Agreement, LLS agreed to provide funding to the Company not to exceed $3.5 million to fund the Company’s development program related to the Company’s preclinical and clinical product development activities. Through September 30, 2018, the Company has received the full $3.5 million based on milestones achieved. Pursuant to the TAP Agreement, the Company shall pay to LLS, subject to the obtaining of certain post-approval milestones, an amount not to exceed three (3) times the dollar amount provided by LLS to the Company. Leases In July 2013, the Company entered into a leasing agreement with respect to its corporate offices at 750 Lexington Avenue, New York, New York, for a monthly rent of $50,625. The term of this lease agreement was 36 months. In February 2016, the Company entered into a new leasing agreement with respect to its corporate offices at 750 Lexington Avenue, New York, New York, for a monthly rent of $69,750 and a 42-month term. The term of this lease agreement commenced on July 1, 2016 and is set to expire on December 31, 2019. The Company extended the lease agreement with the landlord through December 31, 2020. The aggregate minimum lease commitment over the 54-month term of the lease is approximately $3.6 million. The Company has provided the landlord with a security deposit equal to three months’ rent, totaling $209,250, recorded in other assets. In July 2018, the Company entered into a new leasing agreement for additional office space at 750 Lexington Avenue, New York, New York, for a monthly rent of $23,400 and a 12-month term. The term of this lease agreement commences on August 1, 2018 and is set to expire on July 31, 2019. The aggregate minimum lease commitment over the 12-month term of the lease is approximately $0.3 million. The Company has provided the landlord with a security deposit, totaling $39,000. The Company’s future annual minimum lease payments a of September 30, 2018 years are as follows: Remainder of 2018 $ 282,105 2019 1,011,420 2020 847,620 2021 4,425 Total minimum payments $ 2,145,570 Rent expense charged to operations was $709,997 and $598,175 for the nine-month periods ended September 30, 2018 and 2017, respectively. Rent expense is included in general and administrative expenses in the Company’s Statements of Operations. On March 15, 2018, the United States District Court for the Southern District of New York granted a motion to dismiss in its entirety a consolidated shareholder action against the Company, its directors, certain of its officers, and the lead underwriter. On April 11, 2018, Plaintiffs filed a notice of appeal, and on July 13, 2018, the Second Circuit Court of Appeals ordered a withdrawal of the appeal pursuant to Local Rule 42.1. This matter originated from class action lawsuits filed in February 2017 alleging violations of the Exchange Act and Rule 10b-5 promulgated thereunder and violations of Section 11 and 15 of the Securities Act of 1933, or the Securities Act, arising from the Company's January 2017 follow-on public offering. A shareholder derivative litigation was filed in New York Supreme Court in New York County against all of the Company's directors and certain of its officers on May 2, 2017. The consolidated shareholder action was dismissed by the United States District Court for the Southern District of New York on March 15, 2018.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Summary of Significant Accounting Policies
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”), issued a comprehensive new revenue recognition Accounting Standards Update, Revenue From Contracts With Customers (Topic 606) (ASU 2014-09). ASU 2014-09 provides guidance to clarify the principles for recognizing income. This guidance includes the required steps to achieve the core principle that an entity should recognize income 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. This guidance is effective for fiscal years and interim periods beginning after December 15, 2017. Early adoption is permitted for fiscal years and interim periods beginning after December 15, 2016. The Company adopted this guidance on January 1, 2018 using the full retrospective method. The accounting standard had no impact on the financial position, results of operations or cash flows since the Company has no contracts with customers. Any future contracts with customers will be accounted for under the new guidance effective January 1, 2018. As noted below in Note 11 to the Company's Financial Statements, the Company has received grant income from The Leukemia and Lymphoma Society (“LLS”) to fund the Company's development program related to the Company's preclinical and clinical product development activities. The Company has determined that LLS is not a customer as defined by Topic 606. The Company recognizes grant income when there is reasonable assurance of compliance with the conditions of the grant and reasonable assurance that the grant income will be received based on the Company's best estimates of work performed and qualifying costs incurred. In January 2016, the FASB issued a new Accounting Standards Update, Recognition and Measurement of Financial Assets and Financial Liabilities (ASU 2016-01). ASU 2016-01 amends the guidance in U.S. GAAP on the classification and measurement of financial instruments. Although the ASU retains many current requirements, it significantly revises an entity’s accounting related to (1) the classification and measurement of investments in equity securities and (2) the presentation of certain fair value changes for financial liabilities measured at fair value. The ASU also amends certain disclosure requirements associated with the fair value of financial instruments. The new standard is effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2017, with early adoption permitted for certain changes. The Company adopted this guidance on January 1, 2018 and it had no impact on the financial position, results of operations or cash flows. In February 2016, the FASB issued a new Accounting Standards Update , Leases (ASU 2016-02). ASU 2016-02 is aimed at making leasing activities more transparent and comparable and requires most leases be recognized by lessees on the Balance Sheets as a right-of-use asset and corresponding lease liability, regardless of whether they are classified as finance or operating leases. The new standard is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period, with early adoption permitted. The Company is currently evaluating the impact of the new pronouncement on the Company’s financial statements and related disclosures. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230), Classification of Certain Cash Receipts and Cash Payments . ASU 2016-15 clarifies how entities should classify certain cash receipts and cash payments on the Statement of Cash Flows and amends certain disclosure requirements of ASC 230. The guidance will generally be applied retrospectively and is effective for public business entities for fiscal years beginning after December 15, 2017, and interim periods within those years. For all other entities, it is effective for fiscal years beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019. Early adoption is permitted, including adoption in an interim period. If an entity early adopts the guidance in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. An entity that elects early adoption must adopt all of the guidance in the same period. The Company adopted this guidance on January 1, 2018 and it had no impact to the Statement of Cash Flows. In May 2017, the FASB issued ASU No. 2017-09, Compensation - Stock Compensation (Topic 718), Scope of Modification Accounting . ASU 2017-09 provides guidance on the types of changes to the terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting. ASU 2017-09 is applied prospectively to awards modified on or after the effective date. The Company adopted ASU 2017-09 on January 1, 2018. The adoption of this standard did not have a material impact to the Company’s Balance Sheets, Statement of Operations, or Statement of Cash Flows. On December 22, 2017, the Tax Cuts and Jobs Act (the “TCJ Act” or the “Tax Act”) was enacted into law. The TCJ Act provides for significant changes to the U.S. Internal Revenue Code of 1986, as amended (the “Code”), that impact corporate taxation requirements, such as the reduction of the federal tax rate for corporations from 35% to 21% and changes or limitations to certain tax deductions. The reduction in the corporate tax rate under the TCJ Act will also require a one-time revaluation of certain tax-related assets to reflect their value at the lower corporate tax rate of 21%. As such, the Company currently calculates a reduction in the value of these assets of approximately $25.0 million, which is fully offset by a valuation allowance and has no impact on the income tax provision. The company is still evaluating the full impact of the TCJ Act but due to a full valuation against deferred taxes, the company estimates no impact to the income tax provision. On June 20, 2018, the FASB issued ASU No. 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting , which expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. Entities should apply the requirements of Topic 718 to nonemployee awards except for specific guidance on inputs to an option pricing model and the period of time equity awards vest and the pattern of cost recognition over that period. ASU No. 2018-07 is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted and the Company adopted ASU No. 2018-07 on April 1, 2018. The Company early adopted ASU No. 2018-07 on April 1, 2018 and the net impact relating to the adoption was a $0.2 million decrease to accumulated deficit for the impact prior to April 1, 2018. In addition, the Company has elected to account for forfeitures of nonemployee awards as they occur. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements. The ASU allows entities to not recast comparative periods in transition to ASC 842 and instead report the comparative periods presented in the period of adoption under ASC 840. The ASU also includes a practical expedient for lessors to not separate the lease and non-lease components of a contract. The amendments in this ASU are effective in the same time-frame as ASU 2016-02 as discussed above. The Company is incorporating this ASU into its assessment and adoption of ASU 2016-02. In August 2018, the FASB issued ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement”, which adds disclosure requirements to Topic 820 for the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. This ASU is effective for interim and annual reporting periods beginning after December 15, 2019. The adoption of ASU 2018-13 is not expected to have an impact on the Company's financial statements. In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification, amending certain disclosure requirements that were redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expanded the disclosure requirements on the analysis of stockholders' equity for interim financial statements. Under the amendments, an analysis of changes in each caption of stockholders' equity presented in the balance sheets must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed. As such, the Company adopted these SEC amendments on November 5, 2018 and will present the analysis of changes in stockholders’ equity in its interim financial statements in its March 31, 2019 Form 10-Q. The Company does not anticipate that the adoption of these SEC amendments will have a material effect on the Company’s financial position, results of operations, cash flows or shareholders’ equity.

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Prepaid Expenses and Other Current Assets
Schedule of prepaid expenses and other current assets	September 30, December 31, 2018 2017 Prepaid third party vendor costs $ 877,886 $ 131,286 Deferred registration fees — 143,924 Prepaid insurance 250,542 44,065 Deposit 69,660 — Other receivable 798,147 149,792 Total $ 1,996,235 $ 469,067

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2018
Property and Equipment, Net
Schedule of property and equipment, net	September 30, December 31, 2018 2017 Office furniture and fixtures $ 519,675 $ 519,675 Leasehold improvements 82,694 82,694 Capital lease equipment 29,529 — Manufacturing equipment 107,258 13,000 Property and equipment 739,156 615,369 Less accumulated depreciation (517,336) (478,697) Property and equipment, net $ 221,820 $ 136,672

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Measurements
Schedule of the Company's financial assets and liability measured at fair value on a recurring basis	September 30, 2018 Quoted Prices in Active Significant Markets for Other Significant Balance Identical Observable Unobservable at Assets Inputs Inputs September 30, (Level 1) (Level 2) (Level 3) 2018 Assets: Fixed-income treasury portfolio $ 43,051,836 $ — $ — $ 43,051,836 Certificate of Deposits — 23,804,663 — 23,804,663 Cash and cash equivalents 11,677,741 — — 11,677,741 Total assets at fair value $ 54,729,577 $ 23,804,663 $ — $ 78,534,240 December 31, 2017 Quoted Prices in Active Significant Markets for Other Significant Balance Identical Observable Unobservable at Assets Inputs Inputs December 31, (Level 1) (Level 2) (Level 3) 2017 Assets: Fixed-income treasury portfolio $ 40,160,213 $ — $ — $ 40,160,213 Certificate of Deposits — 21,232,813 — 21,232,813 Cash and cash equivalents 4,795,098 — — 4,795,098 Total assets at fair value $ 44,955,311 $ 21,232,813 $ — $ 66,188,124
Summary of cash equivalents and available-for-sale investments held by the Company	September 30, 2018 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains* Losses* Value Cash: Cash from operating accounts $ 7,604,252 $ — $ — $ 7,604,252 Cash equivalents: Money market funds 4,073,489 — — 4,073,489 Total cash and cash equivalents 11,677,741 — — 11,677,741 Short-term investments: Fixed-income treasury portfolio: Fannie Mae 6,655,875 — (6,467) 6,649,408 Federal home loan bank 11,312,471 — (23,642) 11,288,829 Freddie Mac 5,263,336 — (15,376) 5,247,960 U.S. Treasury Securities 19,891,015 — (25,376) 19,865,639 Certificate of Deposits 23,805,052 — (389) 23,804,663 Total short-term investments 66,927,749 — (71,250) 66,856,499 Total $ 78,605,490 $ — $ (71,250) $ 78,534,240 December 31, 2017 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains* Losses* Value Cash: Cash from operating accounts $ 3,088,659 $ — $ — $ 3,088,659 Cash equivalents: Money market funds 1,706,439 — — 1,706,439 Total cash and cash equivalents $ 4,795,098 — — $ 4,795,098 Short-term investments: Fixed-income treasury portfolio: Fannie Mae 13,631,041 — (31,396) 13,599,645 Federal farm credit bank 1,249,823 — (1,869) 1,247,954 Federal home loan bank 5,923,497 — (14,197) 5,909,300 Freddie Mac 5,409,227 — (19,182) 5,390,045 U.S. Treasury Securities 6,282,231 — (12,578) 6,269,653 Others 1,019,302 — (612) 1,018,690 Certificate of Deposits 13,489,241 84 — 13,489,325 Total short-term investments 47,004,362 84 (79,834) 46,924,612 Long-term investments: Fixed-income treasury portfolio: Federal home loan bank 2,753,337 — (15,529) 2,737,808 Freddie Mac 2,509,471 — (13,635) 2,495,836 U.S. Treasury Securities 1,503,030 — (11,748) 1,491,282 Certificate of Deposits 7,743,488 — — 7,743,488 Total long-term investments 14,509,326 — (40,912) 14,468,414 Total $ 66,308,786 $ 84 $ (120,746) $ 66,188,124 *The gross unrealized gains and losses captured in this footnote is before tax.

Accounts Payable and Accrued _2

Accounts Payable and Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2018
Accounts Payable and Accrued Expenses
Schedule of components of accounts payable and accrued expenses	September 30, December 31, 2018 2017 Accrued research and development costs $ 9,188,824 $ 14,805,432 Accrued sales and marketing costs 3,187,821 668,512 Accrued compensation 2,356,275 2,940,039 Accrued general and administrative costs 1,555,056 511,140 Accrued legal 914,114 816,964 Total accounts payable and accrued expenses $ 17,202,090 $ 19,742,087

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2018
Accumulated Other Comprehensive Loss
Schedule of changes in accumulated other comprehensive loss	Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Balance at beginning of period $ (122,973) $ (120,897) $ (145,958) $ (99,802) Other comprehensive income (loss) before reclassification 26,427 30,207 45,515 9,112 Amounts reclassified from accumulated other comprehensive income (loss) — 3,007 3,897 3,007 Total other comprehensive income 26,427 33,214 49,412 12,119 Balance at end of period $ (96,546) $ (87,683) $ (96,546) $ (87,683) *Amounts reclassified affect other income in the Statements of Operations.

Net (Loss) Income Per Common _2

Net (Loss) Income Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2018
Net (Loss) Income Per Common Share
Schedule of computation of basic and diluted net loss per share	Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Basic and diluted net loss per common share calculation: Net loss $ (21,043,996) $ (16,056,147) $ (58,389,451) $ (46,079,093) Basic and diluted weighted-average common shares 29,018,507 23,464,505 28,253,750 22,901,883 Basic and diluted net loss per share $ (0.73) $ (0.68) $ (2.07) $ (2.01)
Schedule of total shares of stock options, restricted stock, and outstanding warrants that could potentially dilute earnings per share in the future, but which were not included in the calculation of diluted net loss per share because their effect would have been anti-dilutive	Nine Months Ended September 30, 2018 2017 Restricted stock 2,631,934 1,796,749 Options outstanding 3,191,018 3,200,211 Warrants — 99,529 Total 5,822,952 5,096,489

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Stock-Based Compensation
Schedule of stock-based compensation by expense category	Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Research and development $ 1,334,967 $ 995,488 $ 3,521,610 $ 2,622,790 General and administrative 1,735,457 1,253,499 5,160,882 3,555,289 Total $ 3,070,424 $ 2,248,987 $ 8,682,492 $ 6,178,079
Schedule of weighted-average key assumptions used in determining the fair value of options granted	Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Weighted-average volatility 75.35 % 75.36 % 76.90 % 75.76 % Weighted-average risk-free interest rate 2.86 % 1.98 % 2.78 % 1.92 % Weighted-average expected term in years 6.26 6.25 6.26 6.07 Dividend yield % % % %
Summary of activity related to the Company's stock options	Weighted- Average Weighted- Remaining Aggregate Average Contractual Intrinsic Options Exercise Price Life Value Outstanding at December 31, 2017 3,174,964 $ 8.74 Options granted 275,000 16.40 Options exercised (169,810) 9.33 Options forfeited (89,136) 17.14 Outstanding at September 30, 2018 3,191,018 $ 9.13 5.96 $ 26,021,455 Options exercisable at September 30, 2018 2,216,605 $ 9.02 5.05 $ 18,841,644
Summary of activity related to the Company's restricted stock	Weighted- Average Grant Date Fair Value Number of Shares Per Share Outstanding at December 31, 2017 1,724,837 $ 7.83 Shares granted 1,496,126 16.83 Shares vested (533,534) 8.42 Shares forfeited (55,495) 11.52 Outstanding at September 30, 2018 2,631,934 $ 12.75

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies
Schedule of future annual minimum lease payments	Remainder of 2018 $ 282,105 2019 1,011,420 2020 847,620 2021 4,425 Total minimum payments $ 2,145,570

Organization and Basis of Pre_2

Organization and Basis of Presentation (Details) - USD ($)	3 Months Ended		9 Months Ended		182 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018
Organization and Basis of Presentation
Net loss	$ (21,043,996)	$ (16,056,147)	$ (58,389,451)	$ (46,079,093)	$ (274,100,000)
Minimum term for which anticipated operating cash requirements are funded			2 years

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($)	Dec. 22, 2017	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of Prospective Application of New Accounting Principle, Net of Tax		$ 200,000
Effect of tax cuts and jobs act of 2017
Statutory tax rate (as a percent)			21.00%	35.00%
Reduction in value of assets	$ 25,000,000
Income tax provision	$ 0
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of Prospective Application of New Accounting Principle, Net of Tax			$ (211,991)
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of Prospective Application of New Accounting Principle, Net of Tax			$ 211,991
ASU 2018-07 | Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of Prospective Application of New Accounting Principle, Net of Tax		(200,000)
ASU 2018-07 | Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of Prospective Application of New Accounting Principle, Net of Tax		$ 200,000

Liquidity and Capital Resourc_2

Liquidity and Capital Resources (Details) $ in Millions	Sep. 30, 2018USD ($)
Liquidity and Capital Resources
Cash, cash equivalents, short and long-term investment balance	$ 78.5

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Prepaid Expenses and Other Current Assets
Prepaid third party vendor costs	$ 877,886	$ 131,286
Deferred registration fees		143,924
Prepaid insurance	250,542	44,065
Deposit	69,660
Other receivable	798,147	149,792
Total	$ 1,996,235	$ 469,067

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Property and Equipment, Net
Office furniture and fixtures	$ 519,675		$ 519,675		$ 519,675
Leasehold improvements	82,694		82,694		82,694
Capital lease equipment	29,529		29,529
Manufacturing equipment	107,258		107,258		13,000
Property and equipment, gross	739,156		739,156		615,369
Less accumulated depreciation	(517,336)		(517,336)		(478,697)
Property and equipment, net	221,820		221,820		$ 136,672
Depreciation expense	$ 14,575	$ 952	$ 38,639	$ 2,856

Fair Value Measurements - Hiera

Fair Value Measurements - Hierarchy (Details) - Recurring basis - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Assets:
Fixed-income treasury portfolio	$ 43,051,836	$ 40,160,213
Certificate of Deposits	23,804,663	21,232,813
Cash and cash equivalents	11,677,741	4,795,098
Total assets at fair value	78,534,240	66,188,124
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Fixed-income treasury portfolio	43,051,836	40,160,213
Cash and cash equivalents	11,677,741	4,795,098
Total assets at fair value	54,729,577	44,955,311
Significant Other Observable Inputs (Level 2)
Assets:
Certificate of Deposits	23,804,663	21,232,813
Total assets at fair value	$ 23,804,663	$ 21,232,813

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Cash Equivalents and Available-for-Sale Investments Held (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Available-for-sale securities
Total Gross Unrealized Gains		$ 84
Total Gross Unrealized Losses	$ (71,250)	(120,746)
Short-term investments
Available-for-sale securities
Amortized Cost	66,927,749	47,004,362
Gross Unrealized Gains		84
Gross Unrealized Losses	(71,250)	(79,834)
Estimated Fair Value	$ 66,856,499	$ 46,924,612
Short-term investments | Maximum
Available-for-sale securities
Remaining contractual maturity	12 months	12 months
Short-term investments | Fannie Mae
Available-for-sale securities
Amortized Cost	$ 6,655,875	$ 13,631,041
Gross Unrealized Losses	(6,467)	(31,396)
Estimated Fair Value	6,649,408	13,599,645
Short-term investments | Federal farm credit bank
Available-for-sale securities
Amortized Cost		1,249,823
Gross Unrealized Losses		(1,869)
Estimated Fair Value		1,247,954
Short-term investments | Federal home loan bank
Available-for-sale securities
Amortized Cost	11,312,471	5,923,497
Gross Unrealized Losses	(23,642)	(14,197)
Estimated Fair Value	11,288,829	5,909,300
Short-term investments | Freddie Mac
Available-for-sale securities
Amortized Cost	5,263,336	5,409,227
Gross Unrealized Losses	(15,376)	(19,182)
Estimated Fair Value	5,247,960	5,390,045
Short-term investments | U.S. Treasury Securities
Available-for-sale securities
Amortized Cost	19,891,015	6,282,231
Gross Unrealized Losses	(25,376)	(12,578)
Estimated Fair Value	19,865,639	6,269,653
Short-term investments | Others
Available-for-sale securities
Amortized Cost		1,019,302
Gross Unrealized Losses		(612)
Estimated Fair Value		1,018,690
Short-term investments | Certificates of Deposits
Available-for-sale securities
Amortized Cost	23,805,052	13,489,241
Gross Unrealized Gains		84
Gross Unrealized Losses	(389)
Estimated Fair Value	$ 23,804,663	13,489,325
Long-term investments
Available-for-sale securities
Amortized Cost		14,509,326
Gross Unrealized Losses		(40,912)
Estimated Fair Value		$ 14,468,414
Long-term investments | Maximum
Available-for-sale securities
Remaining contractual maturity	2 years	2 years
Long-term investments | Federal home loan bank
Available-for-sale securities
Amortized Cost		$ 2,753,337
Gross Unrealized Losses		(15,529)
Estimated Fair Value		2,737,808
Long-term investments | Freddie Mac
Available-for-sale securities
Amortized Cost		2,509,471
Gross Unrealized Losses		(13,635)
Estimated Fair Value		2,495,836
Long-term investments | U.S. Treasury Securities
Available-for-sale securities
Amortized Cost		1,503,030
Gross Unrealized Losses		(11,748)
Estimated Fair Value		1,491,282
Long-term investments | Certificates of Deposits
Available-for-sale securities
Amortized Cost		7,743,488
Estimated Fair Value		7,743,488
Amortized Cost
Available-for-sale securities
Cash and cash equivalents	$ 11,677,741	4,795,098
Estimated Fair Value
Available-for-sale securities
Cash and cash equivalents	11,677,741	4,795,098
Total	78,534,240	66,188,124
Amortized Cost
Available-for-sale securities
Total	78,605,490	66,308,786
Cash from operating accounts | Amortized Cost
Available-for-sale securities
Cash	7,604,252	3,088,659
Cash from operating accounts | Estimated Fair Value
Available-for-sale securities
Cash	7,604,252	3,088,659
Money market funds | Amortized Cost
Available-for-sale securities
Cash equivalents	4,073,489	1,706,439
Money market funds | Estimated Fair Value
Available-for-sale securities
Cash equivalents	$ 4,073,489	$ 1,706,439

Fair Value Measurements - Avail

Fair Value Measurements - Available-for-Sale Securities in Continuous Loss Position (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Fair Value Measurements
Available-for-sale securities in a continuous unrealized loss position for greater than twelve months	$ 0	$ 0

Accounts Payable and Accrued _3

Accounts Payable and Accrued Expenses (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Accounts Payable and Accrued Expenses
Accrued research and development costs	$ 9,188,824	$ 14,805,432
Accrued sales and marketing costs	3,187,821	668,512
Accrued compensation	2,356,275	2,940,039
Accrued general and administrative costs	1,555,056	511,140
Accrued legal	914,114	816,964
Total accounts payable and accrued expenses	$ 17,202,090	$ 19,742,087

Common Stock (Details)

Common Stock (Details)	Jan. 26, 2018USD ($)$ / sharesshares	Jan. 31, 2018USD ($)shares	Jan. 31, 2013$ / sharesshares	Sep. 30, 2018USD ($)Vote$ / sharesshares	Sep. 30, 2017USD ($)	Dec. 31, 2017shares
Net proceeds from offering of shares | $				$ 64,003,764	$ 48,242,214
Number of shares of common stock authorized to be issued | shares				53,750,000		53,750,000
Number of votes to which holders of common shares are entitled for each share held | Vote				1
Number of shares of common stock that may be purchased by warrants | shares		99,529	99,529
Exercisable price of warrants (in dollars per share) | $ / shares			$ 15
Term of warrants			5 years
Proceeds from exercise of warrants | $		$ 400,000		$ 352,528
At-the-Market offering
Net proceeds from offering of shares | $				$ 8,300,000
Issuance of common stock (in shares) | shares				442,579
Share price (in dollars per share) | $ / shares				$ 19.24
Follow on Public Offering
Issuance of common stock (in shares) | shares	3,700,000
Share price (in dollars per share) | $ / shares	$ 14
Over-allotment Option
Net proceeds from offering of shares | $	$ 55,700,000
Share price (in dollars per share) | $ / shares	$ 14
Number of shares issued pursuant to an option granted to the underwriters to cover over-allotments | shares	555,000
Aggregate gross proceeds from public offering | $	$ 59,600,000

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Loss
Balance at beginning of period	$ (122,973)	$ (120,897)	$ (145,958)	$ (99,802)
Other comprehensive income (loss) before reclassification	26,427	30,207	45,515	9,112
Amounts reclassified from accumulated other comprehensive income (loss)		3,007	3,897	3,007
Total other comprehensive income	26,427	33,214	49,412	12,119
Balance at end of period	$ (96,546)	$ (87,683)	$ (96,546)	$ (87,683)

Net (Loss) Income Per Common _3

Net (Loss) Income Per Common Share - Basic and Diluted (Details) - USD ($)	3 Months Ended		9 Months Ended		182 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018
Basic and diluted net loss per common share calculation:
Net loss	$ (21,043,996)	$ (16,056,147)	$ (58,389,451)	$ (46,079,093)	$ (274,100,000)
Basic and diluted weighted-average common shares	29,018,507	23,464,505	28,253,750	22,901,883
Basic and diluted net loss per share (in dollars per share)	$ (0.73)	$ (0.68)	$ (2.07)	$ (2.01)

Net (Loss) Income Per Common _4

Net (Loss) Income Per Common Share - Anti-dilutive Securities (Details) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Net (Loss) Income Per Common Share
Potentially dilutive securities excluded from the computation of earnings per share (in shares)	5,822,952	5,096,489
Restricted stock
Net (Loss) Income Per Common Share
Potentially dilutive securities excluded from the computation of earnings per share (in shares)	2,631,934	1,796,749
Options outstanding
Net (Loss) Income Per Common Share
Potentially dilutive securities excluded from the computation of earnings per share (in shares)	3,191,018	3,200,211
Warrants
Net (Loss) Income Per Common Share
Potentially dilutive securities excluded from the computation of earnings per share (in shares)		99,529

Grant Income (Details)

Grant Income (Details) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended
	Oct. 31, 2013	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Grant Income
Grant income		$ 299,397	$ 500,000	$ 898,199
Leukemia and Lymphoma Society
Grant Income
Grant income			500,000	$ 900,000
Leukemia and Lymphoma Society | Therapy Acceleration Program Agreement
Grant Income
Maximum amount of grants to be received from the Leukemia and Lymphoma Society	$ 3,500,000
Grant proceeds received			$ 3,500,000

Stock-Based Compensation - Equi

Stock-Based Compensation - Equity Incentive Plan (Details) - shares	Jun. 21, 2018	Jun. 30, 2017	Sep. 30, 2018
2016 Plan
Stock Option Plan
Number of common stock shares initially authorized for grant			1,812,932
Increase in number of authorized shares	2,900,000	1,200,000
Number of options with terms in excess of 10 years			0
Term of option			10 years
Shares available for future grants			2,358,480
2012 Plan
Stock Option Plan
Number of common stock shares initially authorized for grant			1,663,727
Number of options with terms in excess of 10 years			0
Term of option			10 years
Shares available for future grants			12,932

Stock-Based Compensation - Expe

Stock-Based Compensation - Expense Category (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock-Based Compensation
Stock-based compensation expense	$ 3,070,424	$ 2,248,987	$ 8,682,492	$ 6,178,079
Research and development
Stock-Based Compensation
Stock-based compensation expense	1,334,967	995,488	3,521,610	2,622,790
General and administrative
Stock-Based Compensation
Stock-based compensation expense	$ 1,735,457	$ 1,253,499	$ 5,160,882	$ 3,555,289

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Options (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Weighted average assumptions used to estimate the weighted average fair value of the options granted on the date of grant using the Black-Scholes option-pricing model
Proceeds from exercise of stock options			$ 1,583,797	$ 7,179
Options
Options exercised (in shares)			(169,810)
Options outstanding
Stock-Based Compensation
Term of option			10 years
Weighted average assumptions used to estimate the weighted average fair value of the options granted on the date of grant using the Black-Scholes option-pricing model
Weighted-average volatility (as a percent)	75.35%	75.36%	76.90%	75.76%
Weighted-average risk-free interest rate (as a percent)	2.86%	1.98%	2.78%	1.92%
Weighted-average expected term in years	6 years 3 months 4 days	6 years 3 months	6 years 3 months 4 days	6 years 26 days
Dividend yield (as a percent)	0.00%	0.00%	0.00%	0.00%
Dividends paid to stockholders			$ 0
Unrecognized compensation expense related to unvested stock options	$ 5,500,000		$ 5,500,000
Weighted average period over which unrecognized compensation expense is expected to be recognized			1 year 9 months 7 days
Options
Outstanding balance at the beginning of the period (in shares)			3,174,964
Options granted (in shares)			275,000
Options exercised (in shares)			(169,810)
Options forfeited (in shares)			(89,136)
Outstanding balance at the end of the period (in shares)	3,191,018		3,191,018
Options exercisable (in shares)	2,216,605		2,216,605
Weighted-Average Exercise Price
Outstanding balance at the beginning of the period (in dollars per share)			$ 8.74
Options granted (in dollars per share)			16.40
Options exercised (in dollars per share)			9.33
Options forfeited (in dollars per share)			17.14
Outstanding balance at the end of the period (in dollars per share)	$ 9.13		9.13
Options exercisable (in dollars per share)	$ 9.02		$ 9.02
Weighted-Average Remaining Contractual Life
Outstanding balance (in years)			5 years 11 months 16 days
Options exercisable (in years)			5 years 18 days
Aggregate Intrinsic Value
Outstanding balance (in dollars)	$ 26,021,455		$ 26,021,455
Options exercisable (in dollars)	$ 18,841,644		$ 18,841,644
Options outstanding | Employees
Stock-Based Compensation
Vesting period			4 years
Options outstanding | Directors
Stock-Based Compensation
Vesting period			3 years

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock-Based Compensation
Net impact of adoption of accounting standard update related to stock compensation accounting (ASU 2018-07)	$ 200,000
Stock-based compensation expense	$ 3,070,424	$ 2,248,987	$ 8,682,492	$ 6,178,079
Non-employees
Stock-Based Compensation
Stock-based compensation expense			$ 1,500,000	500,000
Restricted stock
Number of Shares
Outstanding balance at the beginning of the period (in shares)			1,724,837
Shares granted			1,496,126
Shares vested			(533,534)
Shares forfeited			(55,495)
Outstanding balance at the end of the period (in shares)	2,631,934		2,631,934
Weighted-Average Grant Date Fair Value Per Share
Outstanding balance at the beginning of the period (in dollars per share)			$ 7.83
Shares granted (in dollars per share)			16.83
Shares vested (in dollars per share)			8.42
Shares forfeited (in dollars per share)			11.52
Outstanding balance at the end of the period (in dollars per share)	$ 12.75		$ 12.75
Total aggregate fair value of stock granted			$ 25,200,000
Number of shares remained unvested	2,631,934		2,631,934
Unrecognized compensation expense adjusted for estimated forfeitures, related to unvested restricted stock	$ 28,500,000		$ 28,500,000
Remaining weighted-average period for recognizing unrecognized compensation cost			1 year 11 months 23 days
Total fair value of restricted stock vested			$ 4,500,000	$ 3,000,000
Restricted stock | Directors
Stock-Based Compensation
Vesting period			3 years
Restricted stock | Maximum
Stock-Based Compensation
Vesting period			4 years

Stock-Based Compensation - Empl

Stock-Based Compensation - Employee Stock Purchase Plan (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock-Based Compensation
Stock-based compensation expense	$ 3,070,424	$ 2,248,987	$ 8,682,492	$ 6,178,079
2015 Employee Stock Purchase Plan
Stock-Based Compensation
Stock-based compensation expense			$ 42,275	$ 38,897
2015 Employee Stock Purchase Plan | Minimum
Stock-Based Compensation
Purchase price expressed as percentage of fair market value of common stock on grant date or date of exercise			85.00%
Purchase discount			5.00%

Commitments and Contingencies_2

Commitments and Contingencies (Details)	Jul. 01, 2016USD ($)	Jul. 31, 2018USD ($)	Feb. 29, 2016USD ($)	Jul. 31, 2013USD ($)	Sep. 30, 2018USD ($)item	Sep. 30, 2017USD ($)	Feb. 28, 2013USD ($)
Leases
Monthly lease rent		$ 23,400	$ 69,750	$ 50,625
Lease agreement term	54 months	12 months	42 months	36 months
Security deposit paid to landlord		$ 39,000	$ 209,250
Future annual minimum lease payments
Remainder of 2018					$ 282,105
2,019					1,011,420
2,020					847,620
2,021					4,425
Total minimum payments	$ 3,600,000	$ 300,000			2,145,570
Rent expense					709,997	$ 598,175
Research and development agreements with third parties
Commitments and contingencies
Amount required to be paid upon achievement of certain milestones					217,100,000
Amount paid or accrued					7,000,000
Bioprocessing services agreement
Contractual Agreements
Contractual agreement value							$ 2,900,000
New Service Agreements
Contractual Agreements
Contractual agreement value					28,900,000
Amount paid					24,800,000
Clinical programs with Clinical research organizations (CROs)
Contractual Agreements
Contractual agreement value					4,400,000
Therapy Acceleration Program Agreement | Leukemia and Lymphoma Society
Contractual Agreements
Maximum amount of fund receivable					3,500,000
Grant proceeds received					$ 3,500,000
Maximum times of amount to the dollar amount | item					3