Idelalisib (Zydelig) was once known as CAL-101 and was the most exciting new oral therapy in the CLL world, the shining morning star in the dawn of a new era of treatment for chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL).
While it has been FDA approved for CLL since 2014 as the first PI3K inhibitor blocking the same B cell receptor (BCR) as do the BTK inhibitors, including ibrutinib or acalabrutinib, showing excellent efficacy, its side effects have limited its use.
Its FDA approval in the US for relapsed follicular lymphoma and small lymphocytic leukemia was “accelerated” and conditional on completing further confirmatory trials. However, those trials never accrued, primarily due to new, easily tolerated options.
Gilead gathered blood cancer advocates, including members of the CLL Society, to let us know that they would officially announce that they were formally withdrawing their application for use in relapsed follicular lymphoma and small lymphocytic leukemia.
This was not because of any new concerning safety data or even lack of efficacy. Instead, it was just becoming increasingly clear that these trials would never have enough enrollment to fulfill the standards demanded by the FDA.
Withdrawal of idelalisib from the US market for relapsed FL and SLL does not impact other idelalisib indications. The agent is still FDA approved to treat relapsed chronic lymphocytic leukemia (CLL) in the US and the EU, UK, Canada, Australia, New Zealand, and Switzerland. Idelalisib is also approved in the EU, UK, Canada, Australia, New Zealand, and Switzerland to treat FL.
It could also be used “off label” for FL or SLL, though insurance coverage would need to be assured.
Not really the end of an era, but definitely the end of a dream that this new pill would be the answer for two incurable lymphomas.
Stay strong. We are all in this together.
Brian Koffman MDCM (retired) MS Ed (he, him, his)
Co-Founder, Executive VP, and Chief Medical Officer
CLL Society, Inc.