Since belinostat is not being compared to any other treatment, FDA also considers duration of response to be an important measure of drug efficacy. Celgene's ( CELG) Istodax, which, like belinostat, is an HDAC inhibitor, was approved for patients with advanced PTCL in June 2011 on the basis of a single-arm study with an overall response rate of 26% and a median duration of response of 12 months. Spectrum's Folotyn -- just acquired from Allos Therapeutics -- is also approved for PTCL with an overall response rate (per the drug's label) of 29% with a median duration of response of 10 months. The Folotyn pivotal study was also a single-arm design. "I am sure the FDA will want to look at the complete data picture," said Kapoor, referring to the final response rate and duration of response data from the belinostat study. Spectrum will bring the final belinostat data to a meeting with FDA officials before filing for approval, possibly in 2013, the company said. --Written by Adam Feuerstein in Boston. >To contact the writer of this article, click here: Adam Feuerstein. >To follow the writer on Twitter, go to http://twitter.com/adamfeuerstein. >To submit a news tip, send an email to: email@example.com. Follow TheStreet on Twitter and become a fan on Facebook.