Exhibit 99.1

Onconova Therapeutics Announces Registered Direct Offering

—Gross proceeds to support Phase 3 development of rigosertib in MDS—

NEWTOWN, PA, January 6, 2016 — Onconova Therapeutics, Inc. (ONTX), a clinical-stage biopharmaceutical company focused on discovering and developing novel products to treat cancer, today announced that it has entered into a definitive agreement with a single institutional investor to receive gross proceeds of approximately $1.84 million.

In connection with the offering, the Company will issue approximately 1.9 million registered shares of common stock at a purchase price of $0.95 per share in a registered direct offering.  Additionally, for each share of common stock purchased by the investor, the investor will receive an unregistered warrant to purchase one-half of a share.  The warrants have an exercise price of $1.15 per share, shall be exercisable six months from the date of issuance and will expire five years from the initial exercise date.  The closing of the offering is expected to take place on or about January 11, 2016, subject to the satisfaction of customary closing conditions.

H.C. Wainwright & Co. acted as the exclusive placement agent in connection with this offering.

The shares of common stock described above (but not the warrants or the shares of common stock underlying the warrants) are being offered pursuant to a shelf registration statement (File No. 333-199219) which became effective on November 20, 2014.  Such shares of common stock may be offered only by means of a prospectus, including a prospectus supplement, forming a part of the effective registration statement.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy any of the securities described herein. There shall not be any offer, solicitation of an offer to buy, or sale of securities in any state or jurisdiction in which such an offering, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction. The Company will file a prospectus supplement with the SEC relating to such shares of common stock, and following such filing, copies of the prospectus supplement and the accompanying base prospectus relating to this offering may be obtained at the SEC’s website at http://www.sec.gov, or from H.C. Wainwright & Co. by e-mailing placements@hcwco.com. The warrants and the shares of common stock underlying the warrants issued in the offering have not been registered under the Securities Act of 1933, as amended or applicable state securities laws. Accordingly, the warrants and underlying shares of common stock may not be offered or sold in the United States except pursuant to an effective registration statement or an applicable exemption from the registration requirements of the Securities Act and such applicable state securities laws.

About Onconova Therapeutics, Inc.

Onconova Therapeutics is a Phase 3 clinical-stage biopharmaceutical company focused on discovering and developing novel products to treat cancer. Onconova is currently enrolling patients in a pivotal Phase 3 trial testing its lead compound, rigosertib, in patients with myelodysplastic syndromes (MDS). Onconova’s clinical and pre-clinical stage drug development candidates are derived from its extensive chemical library and are designed to work against specific cellular pathways that are important in cancer cells, while causing minimal damage to normal cells. In addition to rigosertib, the Company’s most advanced product candidate, two other candidates are clinical stage, and several candidates are in pre-clinical stages.  For more information, please visit http://www.onconova.com.

Forward-Looking Statements

Some of the statements in this release are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, Section 21E of the Securities Exchange Act of 1934, as amended, and the Private Securities Litigation Reform Act of 1995, which involve risks and uncertainties. These statements relate to future events or Onconova Therapeutics, Inc.’s future operations, clinical development of Onconova’s product candidates and presentation of data with respect thereto, regulatory approvals, expectations regarding the sufficiency of Onconova’s cash and other resources to fund operating expenses and capital expenditures, Onconova’s anticipated milestones and future expectations and plans and prospects. Although Onconova believes that the expectations reflected in such forward-looking statements are reasonable as of the date made, expectations may prove to have been materially different from the results expressed or implied by such forward-looking statements. Onconova has attempted to identify forward-looking statements by terminology including “believes,” “estimates,” “anticipates,” “expects,” “plans,” “intends,” “may,” “could,” “might,” “will,” “should,” “approximately” or other words that convey uncertainty of future events or outcomes. These statements are only predictions and involve known and unknown risks, uncertainties, and other factors, including Onconova’s need for additional financing and current plans and future needs to scale back operations if adequate financing is not obtained, the success and timing of Onconova’s clinical trials and regulatory approval of protocols, and those discussed under the heading “Risk Factors” in Onconova’s most recent Annual Report on Form 10-K and quarterly reports on Form 10-Q.

Any forward-looking statements contained in this release speak only as of its date. Onconova undertakes no obligation to update any forward-looking statements contained in this release to reflect events or circumstances occurring after its date or to reflect the occurrence of unanticipated events.

Contact

Onconova Therapeutics

Mark Guerin, 267-759-3680

mguerin@onconova.us