Possibly. 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.

Response rates to cancer drugs observed in small studies tend to decrease in larger studies, so I'd be a bit concerned about belinostat being able to maintain a mid-20% response rate in the "BELIEF" study. Spectrum hasn't disclosed whether its agreement with FDA notes a specific response rate that the agency deems approvable.

Since belinostat is not being compared to any other treatment, FDA also considers duration of response to be an important measure of drug efficacy. The five-month response duration seen in belinostat's small phase II study may be too short -- below what, I'd say, is a six-month minimum response duration that the FDA likes to see. (Although to be fair, there is no set threshold.)

Allos Therapeutiucs' ( ALTH) Folotyn 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.

Belinostat stacks up well or not so well against Istodax and Folotyn from an efficacy perspective dependent on which small phase II study you look at. The Spectrum drug may be safer or more easily tolerated, which might work in its favor.

Commercially, belinostat, if approved, is entering a crowded and smallish PTCL market. Folotyn sales totaled only $35 million in the nine months of 2011 ended in September. Istodax sales were $21 million for the same period.

@andu28trader tweets: "Adam still trying to work ARNA to BK I see, you obviously can't interpret the positive data ARNA just released."

By BK, I think "Andu" means bankruptcy. No, I'm not trying to push Arena Pharmaceuticals ( ARNA) into bankruptcy. I am unimpressed with the lorcaserin rat tumor data released this week. It's not going to be enough to persuade U.S. regulators to approve the weight-loss drug later this year.

Arena argues that lorcaserin causes elevations in levels of the hormone prolactin, which is believed to cause mammary tumors (both benign and malignant) in rats but not in humans. The data Arena released this week is designed to convince FDA that the lorcaserin-prolactin link is the cause of the rat tumors and that lorcaserin isn't causing abnormal cell growth through some other unknown mechanism.

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