Peregrine Pharma Cancer Drug Unmasked by Independent Review

TUSTIN, Calif. (TheStreet) --Peregrine Pharmaceuticals' (PPHM) experimental lung cancer drug bavituximab looks like a bust.

Updated results from a mid-state lung cancer study were released Friday morning revealing bavituximab ("bavi") to be not much more than a placebo. Eighty-six lung cancer patients treated with bavi plus carboplatin and paclitaxel (chemo) reported an overall response rate of 25% compared to an overall response rate of 23% for patients treated with carboplatin and paclitaxel alone.

Bavi delayed tumor progression or death by 6.7 months compared to 6.4 months for patients in the control arm -- a difference of just 9 days.

Peregrine shares were down 18 cents, or 20%, to 72 cents in Friday trading.

Friday's disappointing bavi data upend a more positive report from the same study released last December when Peregrine reported a 39% response rate in bavi-treated patients compared to 26% in the control arm.

What happened?

The new results come from a "central" or independent review of the phase II study. When analyzing clinical trial results always give more weight to independent analysis over similar looks at data conducted by investigators actually participating in the trial. Regulators give more weight to independent analysis because it's more objective.

While Peregrine didn't specify, December's results were almost certainly derived from investigators interpreting patient scans. That helps explain why their reported response rates were higher -- and skewed towards bavi. Additional bias is injected into the study because its open label, meaning doctors and patients know who is receiving bavi plus chemo or just chemo alone.

Be extra wary of open-label clinical trials, even those that are randomized and controlled.

You can see further evidence of investigator bias towards bavi in today's progression-free survival results. As I said above, centrally reviewed PFS was essentially identical at 6.7 months for bavi versus 6.4 months for control. Investigator-assessed PFS was 5.8 months for bavi versus 4.6 months for the control arm.

Peregrine says the central review determination of a 6.4-month PFS benefit for the control arm is abnormally high, making the results difficult to interpret. But of course, the central reviewers also came back with a higher PFS for bavi, which the company fails to mention even though it works in their favor.

An assessment of overall survival in this study is pending.

I previously dissected the December results of the bavi study, worth a read because many of the questions I raised turned out to work against Peregrine.

--Written by Adam Feuerstein in Boston.



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Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.