Pfizer’s drug back on the market after proving safety

Back in 2000, Pfizer had a drug that was granted accelerated approval for the treatment of acute myeloid leukaemia (AML) and was continued to be used for 10 years. However, when Pfizer published its supposed confirmatory trial of the efficacy of the drug, they fell short by a long way. The pharma giant was forced into an embarrassing voluntary withdrawal and serious questions were raised about the accelerated approval pathway.

Now, 17 years after its first approval, Mylotarg has been given a second shot. It has been approved for use in adults with newly diagnosed CD33-positive AML, and is also the first therapy to be given an indication in paediatric AML.

The approval was based on the data from several studies, which found Mylotarg alongside chemotherapy to be superior to chemotherapy alone. In particular, the ALFA-0701 trial found that event-free survival for patients receiving Mylotarg and chemotherapy achieved event-free survival of 17.3 months against 9.5 months in patients receiving solely chemotherapy.

Further than this median overall survival was improved in the AML-19 study in patients who were unable to tolerate other AML therapies, with 4.9 months through the use of Mylotarg and 3.6 month with the next-best standard therapy.

Across all uses, Pfizer has revised the recommended dose of the drug – lowering it from previous levels seen in the 2000 approval – and also changing the dosing schedule.

"The FDA approval of Mylotarg fills a critical unmet need for many adults and children with AML, which can be fatal in a matter of months or even weeks if not treated and has a high relapse rate," said Liz Barrett, Global President, Pfizer Oncology. "Based on clinical data, real-world experience and support from the AML community, we are grateful Mylotarg now has the potential to help a broad range of AML patients."