In 2000, Mylotarg (gemtuzumab ozogamicin) became the first antibody-drug conjugate (ADC) to be approved in the US but ten years later it was pulled by Pfizer after subsequent confirmatory trials failed to verify clinical benefit and demonstrated safety concerns, including a high number of early deaths.
But earlier this year, Pfizer resubmitted the product to the US Food and Drug Administration (FDA) and last week it was approved for the same indication - acute myeloid leukaemia (AML) - as well as for patients aged two years and older with CD33-positive AML under a new dosing regimen with a different schedule in combination with chemotherapy, and for a new patient population.
According to Richard Pazdur, director of the FDA’s Oncology Center of Excellence, Mylotarg’s benefits outweigh the risks.
“Mylotarg’s history underscores the importance of examining alternative dosing, scheduling, and administration of therapies for patients with cancer, especially in those who may be most vulnerable to the side effects of treatment.”
The news is the second ADC success in as many weeks for Pfizer after Besponsa (inotuzumab ozogamicin) received US approval for acute lymphoblastic leukaemia in August.
Both ADCs are made at Pfizer’s Pearl River, New York manufacturing facility, a site which was once earmarked for closure following the firm’s megamerger with Wyeth in 2010.
Mylotarg’s reapproval also buoys up the ADC market which has only seen a handful of approvals despite having a commercial presence since 2000.
Pfizer’s Mylotarg and Besponsa join only Genentech’s Kadcyla (ado-trastuzumab emtansine) and Takeda/Seattle Genetics’ Adcetris (brentuximab vedotin).
However there have been a number of large investments in the space from both developers – Jazz Pharmaceuticals and Genmab both recently inked separate ADC R&D deals – and manufacturers. Biopharma firms such as AbbVie and Roche have invested in ADC manufacturing, as have contract manufacturing organisations (CMOs) such as Piramal, ADC Bio and Althea.