UPDATED: Verastem shares crater on Twitter chatter around cancer data

Shares of Verastem ($VSTM) cratered Wednesday morning as the Twitter crowd passed around an abstract on the company's defactinib (VS-6063), highlighting an extremely poor response rate for KRAS mutant non-small cell lung cancer. Fifteen, or 28%, of the patients in the small study hit the PFS endpoint, according to the posted abstract from the 16th World Conference on Lung Cancer, with one partial response.

Three out of four patients, meanwhile, experienced an adverse event, with one in four experiencing a severe reaction, including two grade 5 respiratory failures (meaning they died).

Verastem's shares plunged about 25% on the Twitter reaction, highlighting a growing link between the social media outlet and share prices. The company was founded by Christoph Westphal, now the executive chairman.

A few hours after the stock smash up, Verastem issued a statement saying that the final data from the study was still under embargo for the conference.  But, the company asserted, the full release of data would wind up backing their case for the drug.

"Verastem believes the study has met its goals, with encouraging outcomes that the Company plans to explore in future studies," the biotech says in its statement. "The population explored in this study has refractory, advanced lung cancer, with a median of three prior therapies, and as many as eight prior therapies. The advanced stage of disease led, in some cases, to deaths even in the period between screening and prior to first dose of VS-6063. Two subjects reported as having grade 5 respiratory failure were on multiple concomitant medications and presented with multiple co-morbidities. Both were thoroughly evaluated and reported to the regulatory authorities in 2013 and 2014 when they occurred."

"We can't get ahead of the data," says CEO Robert Forrester in an interview with FierceBiotech. The abstract is based on data that goes back to April with the final release due at the conference in a couple of weeks. And he commented that the safety profile relates to a patient population that is usually dead within an average of 6 months. Forrester says that the study hit the primary endpoint on PFS. Brian Sullivan, the head of corporate communications and business development, also noted that the data monitoring committee on the study has never voiced a problem with the safety data.

The statement did nothing for the biotech's stock, though, ending in the hole 26% at the close.

"It's a little frustrating what happens in the Twittersphere," says the CEO. But he says he'll stay focused on the long run for the company and the drug, rather than a one-day stock reversal.

- here's the release