For many years, the toxicity associated with the first antibody-drug conjugates (ADCs) kept them away from all but the last lines of treatment for a few hematological cancers. But Gilead Sciences, Inc.'s $21bn acquisition of Immunomedics, Inc. and an initial $1.7bn licensing deal between Seattle Genetics, Inc. and Merck & Co., Inc. the following day has brought ADCs back into the spotlight.
The first antibody-drug conjugate, Mylotarg (gentuzumab ozogamicin) for the treatment of refractory acute myeloid leukaemia (AML) − an anti-CD33 monoclonal antibody linked to a cytotoxic payload – was approved 20 years ago under the FDA’s accelerated approval program. Mylotarg’s first ever quarterly sales of $8.8m hinted at a slow start and by the time it was withdrawn from the market because of its unfavorable risk-benefit profile 10 years later, its reported sales in Pfizer Inc.’s annual reports had become even more elusive than a biotech company without a press release related to coronavirus. Mylotarg’s return to the US market in 2017 was at a lower dose, in combination with chemotherapy in newly-diagnosed CD33-positive AML patients, and with analgesic and corticosteroid premedication