Lilly’s Retevmo cleared for RET-positive child cancers

The US FDA has given accelerated approval for Eli Lilly’s RET inhibitor as a treatment for various RET-altered paediatric cancers, making it the first drug in the class available for children aged under 12.

Retevmo (selpercatinib) can now be used to treat RET-positive thyroid cancers and other solid tumours with the mutation, regardless of their type.

Specifically, the new indication covers advanced or metastatic medullary thyroid cancer (MTC) with a RET mutation, advanced or metastatic thyroid cancer with a RET gene fusion that can’t be treated with radioactive iodine therapy, and locally advanced or metastatic solid tumours with a RET gene fusion that have progressed after prior systemic treatment or have no treatment options.

The FDA previously approved the drug to treat RET-positive thyroid cancer in adults and children aged 12 years of age and older, as well as RET-positive solid tumours in adults only. Lilly acquired the drug as part of its $8 billion takeover of Loxo Oncology in 2019.

The new FDA approval is based on the results of the single-arm LIBRETTO-121 study, which included 25 patients aged two to 20 and revealed an overall response rate of 48%, with a median duration of response not reached after 12 months of follow-up. At that time point, 92% of responding subjects remained in response.

The most common adverse reactions seen in more than 25% of patients were musculoskeletal and abdominal pain, diarrhoea, headache, nausea, vomiting and fatigue, and bleeding, among others.

The new approvals will give Retevmo a further lift over its main rival – Blueprint Medicines’ Gavreto (pralsetinib) – which has so far been approved by the FDA for RET-positive thyroid and non-small cell lung cancer (NSCLC).

By far, the majority of RET-positive cancers are lung and thyroid tumours, but the mutations are also found in pancreatic, colorectal, breast, and salivary gland cancers.

Retevmo brought in sales of $254 million last year, up a third on the prior year and well ahead of Gavreto, which was formerly partnered with Roche until it pulled out of the alliance in February. Roche reported sales of $60 million for Gavreto last year, including $28 million from the US market.

Blueprint has now partnered with Rigel Pharma on the product, but in the US only, with the development of marketing of the drug elsewhere not being wound down other than in China where it is licensed to Innovent Biologics and was approved in 2022.