Lilly's RET Inhibitor Gains Accelerated Approval for Pediatric Cancers

The FDA has granted accelerated approval for Eli Lilly’s selective RET kinase inhibitor, Retevmo (selpercatinib), to treat children as young as two years old with specific RET-mutated thyroid and solid tumors. This approval marks a significant milestone as it is the first targeted cancer therapy for pediatric patients under 12 years with RET alterations.

Retevmo has been specifically approved for use in three critical areas: advanced or metastatic medullary thyroid cancer with a RET mutation, advanced or metastatic thyroid cancer with a RET gene fusion in patients who are refractory to radioactive iodine, and locally advanced or metastatic solid tumors with a RET gene fusion in patients who have progressed on a prior systemic therapy. Prior to this, the RET inhibitor already held accelerated approval for treating thyroid cancer in adults and pediatric patients over 12, as well as for solid tumors in adults.

The decision to extend the use of Retevmo to younger patients was supported by data from the Phase I/II LIBRETTO-121 study. This study involved 25 pediatric patients aged between 2 to 20 years who had locally advanced or metastatic RET-activated solid tumors that did not respond to existing treatments. The results of the study showed a confirmed overall response rate (ORR) of 48%. Notably, the median duration of response (DOR) was not reached, with 92% of responders still experiencing the treatment's effects at 12 months.

In terms of safety, the most common adverse reactions observed in more than 25% of patients included musculoskeletal pain, diarrhea, headache, nausea, vomiting, and fatigue. These side effects were relatively consistent with those previously observed in older patients, indicating a manageable safety profile for pediatric use.

Eli Lilly acquired Retevmo through its $8-billion acquisition of Loxo Oncology in 2019. This strategic acquisition enabled Lilly to expand its portfolio in targeted cancer therapies, focussing on rare and genetically defined cancers. The recent FDA approval underscores the potential of Retevmo in addressing unmet medical needs in pediatric oncology, particularly for conditions with limited treatment options.

In conclusion, the FDA's accelerated approval of Retevmo for children aged two and above with specific RET-mutated cancers represents a significant advancement in pediatric cancer treatment. With its promising efficacy and manageable safety profile, Retevmo offers new hope for young patients battling these challenging conditions.