Peregrine Pharma's Lung Cancer Drug: Boffo Survival Benefit, But How Real?

TUSTIN, Calif. ( TheStreet) --The results presented Friday on Peregrine Pharmaceuticals' ( PPHM) lung cancer drug bavituximab -- a jaw-dropping doubling of survival compared to a control arm -- were spectacular. But are the data from the midstage study credible?

Every cell in my body screams, "No!!!" The idea that Peregrine, a dismissed biotech penny stock as recently as two months ago, might be sitting on one of the most effective lung cancer drugs ever developed, doesn't just strain credulity, it beats credulity to death with a baseball bat.

Still, Peregrine's bavituximab lung cancer data look awesome. Second-line nonsmall-cell lung cancer patients treated with a combination of bavituximab and docetaxel reported a median overall survival of 12.1 months compared to 5.6 months for patients treated with docetaxel and a placebo.

That's a six-month improvement in survival or a statistically significant, 50% reduction in the risk of death. Cancer drugs that double survival or halve the risk of death are rare. They don't exist in lung cancer. Avastin, Roche's ( RHHBY) $7 billion-per-year cancer uber-drug, improves first-line lung cancer survival by two months.

Peregrine may well have a blockbuster lung cancer drug on its hands. The possibility can't be denied outright. But as a die-hard biotech skeptic, I'm not going to be fully convinced until Peregrine produces a lot more answers. Neither should you.

I want to see data that parse bavituximab's response rate and overall survival by geography. The phase II study enrolled half of its 117 patients in Russia, Ukraine, the Republic of Georgia and India -- geographies with a reputation for producing overly positive results that cannot be reproduced in later, larger confirmatory trials.

The remaining 50% of patients came from the U.S. Not to sound xenophobic, but data culled from U.S.-based centers carry more weight and are less likely to be biased.

Survival is a hard endpoint to fudge -- a patient is either dead or they're not -- so fabricating survival results isn't the biggest concern. I'm more worried about Eastern European or Indian doctors enrolling lung cancer patients who haven't yet truly failed first-line therapy and therefore shouldn't be eligible for the second-line bavituximab study. Peregrine's study is small enough that a handful of relatively healthy patients living longer could have skewed survival results.

This is not just a theoretical risk. Doctors are paid to enroll patients in clinical trials, and that cash is especially welcome in Eastern Europe and India. And patients in these countries will do just about anything to participate in clinical trials because they receive free drugs and medical treatment. Targacept ( TRGT), Cell Therapeutics ( CTIC) and Medivation ( MDVN) have all been torpedoed in the past by less-than-rigorous conduct of clinical trials outside the U.S. and Western Europe.

The credibility of Peregrine's second-line bavituximab study will be bolstered if tumor response and the survival benefit are comparable between U.S. patients and those treated in Eastern Europe and India. The company can easily produce these data, but they were missing from Friday's presentation.

Bavituximab might also win over skeptics if the drug can repeat its survival benefit feat in another lung cancer clinical trial. Thankfully, we only have to wait until the end of the year for the answer.

Peregrine is conducting a separate randomized, controlled phase II study in treatment-naive, or first-line, lung cancer patients. The 86 patients in the study are randomized to receive bavituximab added to the chemotherapy "doublet" of carboplatin and paclitaxel or the chemo doublet on its own.

Initial results from this front-line lung cancer study were released last March, and they weren't positive. The tumor response rate in the bavituximab arm was 25% compared to 23% for the control arm; progression-free survival was 6.7 months for bavituximab vs. 6.4 months in the control arm -- a difference of just nine days.

Peregrine says wait for survival results before calling the front-line lung study a failure. Bavituximab works by attaching to a molecule found on tumor blood vessels that acts like shield against the immune system. By blocking this immune-suppressing molecule known as phosphatidylserine (PS), a patient's immune system is able to target and kill cancer cells.

Broadly speaking, bavituximab is supposed to be an immune-stimulating cancer drug like Dendreon's ( DNDN) Provenge and Bristol-Myers Squibb's ( BMY) Yervoy. A common trait supposedly shared by cancer immunotherapies is a modest antitumor response followed by a delayed survival benefit. It takes the immune system longer to target and kill tumor cells.

If bavituximab truly doubles lung-cancer survival in the second-line setting, the drug should demonstrate a similar benefit in the front line.

Peregrine's first-line lung cancer study also enrolled roughly half its patients from Eastern Europe and India, so the same need to show geographic consistency applies.

A previously reported single-arm study of bavituximab plus carboplatin/paclitaxel in 49 first-line lung cancer patients -- all recruited from India -- reported an overall response rate of 43%, median progression-free survival of 6.1 months and a median overall survival of 12.4 months.

Comparing across trials is problematic, but it does seem strange that bavituximab is producing a lung cancer survival benefit in the second line (12.1 months) equivalent to the first line (12.4 months). One possible explanation, of course, is that the patients enrolled in the second-line study presented Friday aren't really second-line patients.

One more question regarding bavituximab's purported mechanism of action: If the drug is indeed an immune-stimulatory anticancer drug, shouldn't there be clinical data related to immune response and/or associated toxicity? I can't recall seeing any such data.

Peregrine is holding a conference call Monday morning to discuss Friday's bavituximab data. Peregrine shares closed Friday up $1.43, or 47%, to $4.50.

-- 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.

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