Renaissance for Pfizer antibody-drug conjugate?

Pfizer has scored a phase III trial success for its antibody-drug conjugate (ADC) inotuzumab ozogamicin in acute lymphoblastic leukaemia (ALL), two years after the drug was all-but written off.

The CD22-targeting drug – partnered with Belgian company UCB – failed to show any impact on overall survival in a trial involving patients with an aggressive form of non-Hodgkin lymphoma in 2013.

Now, interim data from the INO-VATE ALL study suggest the ADC can improve haematological remission rates versus chemotherapy, although it will be some months before its impact on survival will be seen.

The open-label trial enrolled 325 patients with CD22-positive ALL who were randomised to receive either inotuzumab ozogamicin or chemotherapy with fludarabine, cytarabine and G-CSF (FLAG), high dose cytarabine or cytarabine plus mitoxantrone.

It is not due to complete follow-up until March 2017, according to its registry entry on clinicaltrials.gov – although Pfizer chief medical officer Mace Rothenburg said the company was looking forward to discussing the remission rate data with the US FDA and other regulatory authorities.

"The top-line results show that inotuzumab ozogamicin has the potential to be an important new treatment option for patients with relapsed or refractory disease," he said.

Approximately 20 to 40 per cent of newly-diagnosed adults with ALL are cured with current treatment regimens, but for those with relapsed or refractory disease, the five-year overall survival rate is less than 10 per cent.

If inotuzumab ozogamicin can show an overall survival benefit it could give Pfizer's oncology group another win after gaining an earlier-than-expected approval for Ibrance (palbociclib), its first-in-class cyclin-dependent kinase (CDK) 4 and 6 inhibitor.

The company has also just received a breakthrough designation for its ALK inhibitor Xalkori (crizotinib) for the potential treatment of patients with ROS1-positive non-small cell lung cancer (NSCLC), while earlier this week it took PD-L1 inhibitor avelumab (MSB0010718C) - partnered with Merck KGaA - into a phase III trial in advanced NSCLC.

The NSCLC trial is the first of several registration trials due to start this year for avelumab as it tries to close the gap with the leaders in the PD-1/PD-L1 inhibitor category, Bristol-Myers Squibb and Merck & Co.