4. Warrants

Common stock warrants are accounted for in accordance with applicable accounting guidance provided in ASC Topic 815, Derivatives and Hedging-Contracts in Entity’s Own Equity (ASC Topic 815), as either derivative liabilities or as equity instruments depending on the specific terms of the warrant agreement. Some of the Company’s warrants are classified as liabilities because in certain circumstances they could require cash settlement.

Warrants outstanding at December 31, 2017 and 2018, and warrant activity for the year ended December 31, 2018 is as follows (reflects the number of common shares as if the warrants were converted to common stock):


					Balance				Balance
		Exercise		Expiration	December 31,	Warrants	Warrants	Warrants	December 31,
Description	Classification	Price		Date	2017	Issued	Exercised	Expired	2018
Non-tradable warrants	Liability	$	172.50	July 2021	6,456	—	—	—	6,456
Tradable warrants	Liability	$	73.80	July 2021	212,801	—	—	—	212,801
Non-tradable pre-funded warrants	Equity	$	0.15	July 2023	394	—	—	—	394
Non-tradable warrants	Equity	$	6.69375	*	—	663,167	—	—	663,167
Non-tradable warrants	Equity	$	7.96875	*	—	33,158	—	—	33,158
Non-tradable warrants	Equity	$	14.10	March 2021	—	5,000	—	—	5,000
Non-tradable warrants	Equity	$	21.15	March 2021	—	8,333	—	—	8,333
Non-tradable warrants	Equity	$	7.7895	June 2021	—	15,000	—	—	15,000
Non-tradable pre-funded warrants	Equity	$	0.15	none	—	196,167	(110,000)	—	86,167
Non-tradable warrants	Equity	$	6.375	**	—	4,509,804	(76,842)	—	4,432,962
Non-tradable pre-funded warrants	Equity	$	0.15	none	—	815,686	(553,618)	—	262,068
					219,651	6,246,315	(740,460)	—	5,725,506

* These preferred stock warrants expire on the earlier of (A) the one-month anniversary of the date on which the Company publically releases topline results of the INSPIRE Pivotal phase 3 that compare the overall survival (OS) of patients in the rigosertib group vs the Physician’s Choice group, in all patients and in a subgroup of patients with IPSS-R very high risk and (B) December 31, 2019. These preferred stock warrants may be exercised on a cashless basis in certain circumstances specified therein.

** These preferred stock warrants expire on the 18-month anniversary of June 8, 2018, the date on which the Company publicly announced through the filing of a Current Report on Form 8-K that a Certificate of Amendment to the Company’s Tenth Amended and Restated Certificate of Incorporation, as amended, to increase the number of authorized shares of common stock from 100,000,000 to 250,000,000, was filed with the Secretary of State of the State of Delaware. These preferred stock warrants may be exercised on a cashless basis in certain circumstances specified therein.