Pfizer’s (NYSE:PFE) inotuzumab ozogamicin faces an uncertain path to FDA approval in acute lymphoblastic leukemia (ALL) following mixed Phase III trial results, experts said.
While experts said the INO-VATE ALL study (NCT01564784) results still keeps approval hopes alive, reservations persist. In addition, the data drew mixed opinions from biostatisticians, with one saying a post-hoc analysis of overall survival (OS) using restricted mean survival time (RMST) was proper and indicated a positive result, while two others expressed skepticism because it was not pre-specified in the analysis.
Results from the 326-patient study were published in August (Kantarjian, et al. N Engl J Med 2016;375:740-53), demonstrated the study met the primary endpoint of complete remission (CR) rate over six months, but not OS over 24 months. The post-hoc analysis, using RMST, nevertheless showed an OS benefit. Inotuzumab ozogamicin is a CD22-targeting antibody-drug conjugate (ADC) and has an FDA breakthrough therapy designation.
A Pfizer spokesperson said the company is working closely with the FDA and other regulatory authorities to make the drug available in relapsed or refractory adult ALL that is CD22-positive, she noted. The drug originates from a collaboration between Pfizer and UCB (EBR:UCB), with Pfizer taking full responsibility for manufacturing and clinical development.