Stock nosedives for cardiovascular drugmaker Arca following Phase IIb AF failure

A small biopharma near Denver is watching its stock plunge following news that its Phase IIb heart drug was a bit of a bust. The atrial fibrillation drug, Gencaro, failed to perform any better than the study’s control.

Michael Bristow

The company, Arca Biopharma, took a red herring approach to its news release, focusing hard on its data for the US population rather than the overall study.

The trial, called GENETIC-AF, was testing Gencara (bucindolol hydrochloride) as a genetically-targeted treatment for AF in patients with heart failure and reduced ventricular ejection fraction. The active control was a drug called metoprolol succinate (Toprol-XL).

In a statement, Arca highlighted a “trend for potential superior benefit” in US patients:

In US patients (127 of 267 total patients), a trend for potential superior benefit in favor of Gencaro (approximately 30% risk reduction over Toprol-XL), was observed for the primary endpoint of time to recurrence of AF. Additionally, in US patients, Gencaro demonstrated a trend for potential superior benefit in favor of Gencaro (approximately 51% risk reduction over Toprol-XL) in a subset of patients who underwent continuous heart rhythm monitoring with Medtronic implanted devices.

Despite their cheery press release, investors aren’t fooled. The company’s stock $ABIO was down 56% in pre-market trading.

That’s because the study’s goal was to show Arca’s drug was better than Toprol-XL in its entire patient group, which included 267 patients from the US, Canada, and Europe.

In Arca’s press release, it notes that the drug only showed similar benefit to Toprol-XL, not superiority. According to the study’s description, that’s considered a failure:

The goal of the GENETIC-AF trial is to demonstrate the superiority of pharmacogenetically targeted bucindolol compared to metoprolol for the prevention of symptomatic atrial fibrillation or atrial flutter in a genotype-defined population with heart failure and/or reduced left ventricular ejection fraction at high risk of atrial fibrillation/atrial flutter recurrence.

Arca is putting on a brave face, however, charging towards a Phase III trial design, according to its press release.

“While we did observe some regional heterogeneity in effectiveness of Gencaro, we believe the treatment response observed in the US population, which represents approximately half of the overall study population, support continued development of Gencaro as a genetically-targeted treatment for atrial fibrillation,” said Michael Bristow, ARCA’s president and CEO, in a statement. “As in all Phase II trials, which in part are conducted to elicit information relevant to the design for Phase III, elucidation of the reason(s) for regional heterogeneity could prove valuable for Phase III trial design.”

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