Merck's Keytruda scores solo lymphoma nod, but analysts are fixed on Seagen's combo potential

Merck & Co.’s Keytruda has won a new place on the previously treated classical Hodgkin lymphoma (cHL) market—but now it has to carve out market share. And long-term, that may not be so easy against Seagen’s Adcetris, despite a head-to-head win in Merck’s favor.

The FDA Thursday cleared the anti-PD-1 med as a second-line therapy for adult cHL patients with relapsed or refractory disease, making it the first in its class with that distinction. The agency based the OK on data showing Keytruda could cut patients’ risk of disease progression or death by 35% against Adcetris, helping patients live a median 13.2 months before their cancer worsened, compared with 8.3 months for Seagen’s drug.

That difference is "really quite striking," as Roy Baynes, M.D., Merck's senior vice president and head of global clinical development, put it ahead of the data’s release at the American Society of Clinical Oncology virtual annual meeting.

RELATED: ASCO: Merck's Keytruda thumped SeaGen's Adcetris in a head-to-head trial. How much does it matter?

Analysts, though, seem less interested in a monotherapy showdown than they are in forthcoming combo results, which they predict will boost Adcetris considerably.

Seagen is testing the drug in tandem with Bristol Myers Squibb’s Opdivo—Keytruda’s PD-1 archrival—and early data has shown the duo can produce a response rate above 90%, which is “vastly superior” to both Adcetris and checkpoint inhibitors given as monotherapies, SVB Leerink analyst Andrew Berens wrote in a March note to clients.

“Adcetris is unlikely to concede that segment” to solo checkpoint drugs, he added, with JPMorgan’s Cory Kasimov predicting in his own March note that the ongoing study “may establish the combination as the regimen of choice.”

Of course, Seagen doesn’t yet have the data to do that, as Merck’s Baynes pointed out in May.

RELATED: Merck's Keytruda nabs first blood-cancer nod, but rare cancer decision has to wait

"Most of the combination data that has been produced is single-arm data, so it’s not randomized. We really don’t know how reliable those findings will be when studied in a randomized fashion," he said.

But the Seagen drug does have an approval in the wider population of previously untreated patients, something Keytruda can’t say. Kasimov’s prediction? "Adcetris continues to gain traction in the front line (where Merck is notably absent) and is used in combination with PD-1s in the relapsed/refractory setting,” he wrote.

Meanwhile, Merck's win over Adcetris in the Keynote-204 trial did something else for Keytruda, aside from setting it up for a Seagen market showdown. The results confirmed the benefits that led the FDA to grant the drug an accelerated approval for adult and pediatric patients who have relapsed after three or more prior treatments, meaning the therapy is now eligible for a full approval.