UPDATED: PhII flop clouds future of Amgen, Cytokinetics heart failure drug

Cytokinetics shares ($CYTK) took a dive in early trading today after its partner Amgen ($AMGN) reported that an IV formulation of their heart failure drug omecamtiv mecarbil failed a key Phase IIb trial, just weeks after Amgen paid $25 million to expand their licensing pact. And investigators say they'll wait for a read-out on the data from a Phase II study of an oral version of the drug before deciding whether to green-light a Phase III program or scrap the effort.

Cytokinetics' stock plunged 29% on the news.

Omecamtiv emerged from a longstanding partnership between Cytokinetics and Amgen. The biotech's original notion that a protein found in heart cells--cardiac myosin--could be activated to amp up the rate of heart contractions inspired an ambitious development effort. But in this initial Phase II trial--which recruited 613 patients--the data reflected no statistically significant improvement in shortness of breath, a condition known as dyspnea, when compared to pooled placebo data.

But that didn't stop Amgen, which has been working to expand its drug portfolio, from reading the data in the best light possible.

In the highest dose used in the study, investigators found that 51% of patients taking the drug experienced an improvement in shortness of breath compared to 37% of the patients in the paired placebo arm (distinct from the pooled placebo response data, which TheStreet reports was 41%). That subset breakout gave Amgen cause for hope--or at least some solid ground to put a positive spin on a trial failure.

In June, Amgen bought $25 million worth of Cytokinetics' shares and offered up to $50 million in milestones to expand their licensing deal to include Japan.

Both Reuters and Bloomberg turned to Duke's heart expert Dr. Christopher Granger, who was not involved in the study, for a response. He made it clear that the data leave this therapy under a cloud for now. "I would be discouraged by this in terms of the implications for the drug having an important effect," Granger told Reuters' Ben Hirschler.

But not everyone was equally skeptical. Cowen's Simos Simeonidis noted that the lowest dose group was "sub-therapeutic," likely skewing the efficacy data. And the top-dose group looked good, giving Simeonidis cause for hope, especially when you add the likelihood that Amgen had seen the data from the study before it signed the expanded licensing deal.

Amgen also noted that "the incidence of worsening heart failure within seven days of initiating treatment was 17% in the pooled placebo group and was 13%, 8% and 9% on omecamtiv mecarbil in the first, second and third cohorts, respectively. Systolic ejection time, the echocardiographic signature of omecamtiv mecarbil, increased in a concentration-dependent manner."

"Although ATOMIC-AHF did not achieve its primary efficacy endpoint, we are encouraged by the data from this study," said Amgen R&D chief Sean E. Harper. "Omecamtiv mecarbil is a unique investigational therapy for patients with acute and chronic heart failure. We look forward to the data from the COSMIC-HF study, which together with the data from ATOMIC-AHF will inform our decision on whether to progress omecamtiv mecarbil into Phase III clinical trials."

- here's the press release
- here's the Bloomberg report
- here's the Reuters story
- here's the report from TheStreet