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

Merck’s Keytruda has taken on the standard of care in classical Hodgkin lymphoma and won. But with a closely watched combination making its way through the clinic, how long will the results be relevant? Depends who you ask.

Compared with Seattle Genetics' Adcetris, Merck’s PD-1 star cut the risk of disease progression or death by 35% among patients with relapsed or refractory disease, the New Jersey drugmaker said ahead of the American Society of Clinical Oncology (ASCO) virtual annual meeting. 

Patients receiving Keytruda as part of the study, called Keynote-204, went a median 13.2 months before their cancer worsened, compared with 8.3 months for those in the Adcetris group. That's "really quite striking," said Roy Baynes, M.D., Merck's senior vice president and head of global clinical development.

About one-fifth of Hodgkin patients will relapse after their initial therapy or not go into remission at all, he added, and "typically that's been a difficult group of patients to treat."

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The thing is, as analysts see it, it may not be all that long before monotherapies in the relapsed and refractory setting are knocked aside by a combination approach—specifically, the combination of Adcetris and Keytruda’s archrival, Bristol Myers Squibb’s Opdivo. That pairing has posted a response rate of more than 90%, a performance “vastly superior to both drugs given as monotherapies,” Leerink Partners’ Andrew Berens wrote in a note to clients following the pharma giant’s top-line release.

“An ongoing study testing Adcetris plus Opdivo versus Adcetris alone may establish the combination as the regimen of choice,” he added.

JPMorgan's Cory Kasimov echoed those sentiments, writing to his own clients with a prediction that "Adcetris continues to gain traction in the front line (where Merck is notably absent) and is used in combination with PD-1s" in patients who've relapsed or proven resistant to treatment.

But as Baynes pointed out, that combination has a ways to go in the clinic before it can displace monotherapy. "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, also noting that Keytruda monotherapy was well tolerated among study patients.

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Merck had a goal with the study other than wresting share from Seattle Genetics, though. It will serve as a confirmatory trial for the accelerated approvals Keytruda won in hematology—including one in classical Hodgkin lymphoma for patients who have relapsed after three or more prior lines of therapy—and the company plans to submit the data to regulators later this year.