July 23, 2013


United States Securities and Exchange Commission
Division of Corporation Finance
100 F Street, N.E.
Washington, DC  20549



Jeffrey P. Riedler, Assistant Director


Austin Stephenson


Dan Greenspan


Jim Peklenk


Mark Brunhofer


Re:                             Onconova Therapeutics, Inc.

Registration Statement on Form S-1 (File No. 333-189358)


Ladies and Gentlemen:


In connection with the above-captioned Registration Statement, we wish to advise that between July 11, 2013 and the date hereof 1,170 copies of the Preliminary Prospectus dated July 11, 2013 were distributed as follows: 220 to prospective underwriters; 790 to institutional investors; 0 to prospective dealers; 160 to individuals; 0 to rating agencies and 0 to others.


We have been informed by the participating underwriters that they will comply with the requirements of Rule 15c2-8 under the Securities Exchange Act of 1934, as amended.


We hereby join in the request of the registrant that the effectiveness of the above-captioned Registration Statement, as amended, be accelerated to 4:00 p.m. Eastern Time, on Wednesday, July 24, 2013 or as soon thereafter as practicable.


[signature page follows]



Very truly yours,


Citigroup Global Markets Inc.

Leerink Swann LLC

As representatives of the

Prospective Underwriters



Citigroup Global Markets Inc.






/s/ Brian Gleason



Name: Brian Gleason


Title: Director






Leerink Swann LLC






/s/ Daniel Dubin



Name: Daniel Dubin


Title: Vice Chairman


Signature Page to Acceleration Request