Pfizer's tafamidis score still leaves 'door open' for Alnylam rival: analysts

Pfizer sign
Twenty milligram data for Pfizer's tafamidis are "not as impressive" as Alnylam's in neuropathy patients, Evercore ISI analysts wrote. (Tracy Staton)

Pfizer may have impressed pharma watchers Monday with its blockbuster data on transthyretin cardiomyopathy candidate tafamidis. But that doesn’t mean Alnylam and its newly approved Onpattro are suddenly out of the running.

Pfizer’s data showed tafamidis cut mortality by 30% and cardiovascular-related hospitalizations by 32% in patients with the condition, also known as ATTR-CM, a form of the rare disease transthyretin amyloidosis (ATTR). That was “better than what physicians and investors … were expecting,” Credit Suisse analyst Vamil Divan wrote in a note to clients, calling the results “practice-changing.”

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But the data also left “the door open” to Onpattro in a future showdown with tafamidis, Evercore ISI analysts Josh Schimmer and Steve Breazzano wrote in a note to clients. The Alnylam drug is now approved for hereditary ATTR polyneuropathy, but it’s headed for the same cardiomyopathy market—and likely to face Pfizer eventually in polyneuropathy, too, the analysts noted.

In fact, Pfizer’s data could end up helping the Alnylam med. “Tafamidis data demonstrated the drug is beneficial, but … there are some weaknesses” that “ultimately should enhance Onpattro's commercial opportunity,” Jefferies analyst Maury Raycroft agreed in his own investor note. And investors apparently agreed, too: They sent Alnylam’s shares skyward on Monday.

RELATED: Alnylam vows value-based pricing, financial help with $450K Onpattro launch

One of the weaknesses that could boost Onpattro? Upping the dose of tafamidis to 80 mg from 20 mg didn’t yield stronger results, meaning 20 mg “is as good as it gets,” Raycroft noted. And to the Evercore analysts, that may not be good enough to take on Onpattro in neuropathy patients.

“In our eyes, the 20 mg tafamidis data is not as impressive” as Alnylam’s in that population, they wrote.

Tafamidis also didn’t turn up a statistically significant benefit in patients with the hereditary form of ATTR, which is the form Onpattro is approved to treat.

That doesn’t mean it’ll necessarily be smooth sailing for Alnylam from here on out, though. Tafamidis shined in the larger, wild-type subpopulation of ATTR-CM patients, where the RNAi-focused biotech intends to test another candidate, TTRsc02, down the line. And given how long it took for tafamidis to begin showing benefit—it started paring down the mortality numbers after the 18-month mark—“it may not be a quick path,” Evercore’s analysts wrote.

Instinet analyst Christopher Marai was even less optimistic, writing that Alnylam has a “large, long, and risky cardiac trial ahead.”

“The scope and length of a trial head-to-head with tafamidis or against placebo would be five-plus years, by our estimates,” he said, adding that “cardiac trials are notoriously difficult.”