FDA approval for Tafasitamab-cxix for R/R FL

The FDA has approved Tafasitamab-cxix (also known as Monjuvi) in combination with Lenalidomide (also known as Revlimid) and Rituxan for Relapsed/Refractory Follicular Lymphoma.

I wrote about this combination in November, just before the ASH conference. The results of a phase III clinical trial were being presented at ASH, and the website Fierce Pharma called the early results a "triumph." The makers of Tafasitamab had said immediately afterwards that they were going to seek FDA approval. And it came.

Tafasitamab had already been approved by both the FDA and the EU for use on R/R Diffuse Large B Cell Lymphoma, in combination with Lenalidomide.

Tafasitamab is a monoclonal antibody, like Rituxan. But Tafasitamab targets a different protein, CD19, on the surface of B cells (Rituxan targets CD20). The idea was that combining the two (along with Lenalidomide) would increase the chances that the treatment could find the cancer cells. That seems to have been the case.

The trial involved a direct comparison between Tafasitamab + Lenalidomide + Rituxan and a placebo + Lenalidomide + Rituxan. In other words, patients in the trial were going to receive either this new combination or just R-squared (Lenalidomide/Revlimid + Rituxan). Patients in the trial had already received at least one treatment for their FL already.

As Fierce Pharma said, the results were triumphant. After a median follow up of 14.1 months, the Progression Free Survival for the Tafasitamab combination was 22.4 months and 13.9 months in the other group. The Complete Response Rate was 49.9% for Tafasitamab and 39.8% for the other group, and the Overall Response Rate was 83.5% vs 72.4%.

The question with the combination was going to be about safety. Monoclonal antibodies like Tafasitamab and Rituxan work by eliminating B Lymphocytes, a kind of immune cell. They target both healthy B cells and cancerous B cells. So while having two antibodies targeting the same cells might mean it's more effective, it also means you're running the risk f having too many immune cells being disabled all at once, opening up the possibility of greater risk of infections.

And that did happen. In their announcement, the FDA points out that "serious adverse reactions occurred in 33% of patients" in the Tafasitamab group, including serious infections in 24% of participants.The announcement doesn't give a direct comparison to the other group in the trial, though the ASH presentation did -- 36% of the Tafasitamab group vs 32% for the other group (the FDA numbers are a little different because they were updated 6 months later). Also in the ASH presentation, it was noted that during the study, 15 patients in the Tafasitamab group died, 5 because of disease progression and 6 because of side effects, versus 23 in the other group (17 due to disease progression and 6 from side effects). 

It will be interesting to see how popular this combination becomes with oncologists. Will this become a substitute for R-Squared? Similar way of working, but more effective? Or will some patients still be given R-squared instead because it seems slightly less aggressive on the immune system? (Remember, I'm not a medical doctor -- these are just questions that are coming to me immediately after reading this). I look forward to reading more commentaries in the coming weeks and months.