Retevmo (selpercatinib) Treatment of Lung and Other “RET Fusion” Cancers
by Dr. C.H. Weaver M.D. updated 9/2020
Retevmo (selpercatinib -LOXO-292), a novel precision cancer medicine targeting tumors containing a mutated protein known as RET was approved by the US Food and Drug Administration in May 2020. Retevmo is approved for the treatment of non-small cell lung cancers (NSCLC) and other cancers with RET mutations identified by NGS testing.
About Retevmo (selpercatinib-LOXO-292)
Retevmo is an oral precision cancer medicine that is designed to target cancers with genomic alterations in the RET kinase, which include fusions and activating point mutations which lead to overactive RET signaling and uncontrolled cell growth. These “RET fusions” have been identified in approximately 2% of non-small cell lung cancer, 10-20% of papillary and other thyroid cancers, and a subset of other cancers. Activating RET point mutations account for approximately 60% of medullary thyroid cancer. Retevmo was designed to inhibit native RET signaling as well as anticipated acquired resistance mechanisms that could otherwise limit the activity of this therapeutic approach.
In the initial clinical trial of Selpercatinib it shrank the cancer in 77% of patients with RET fusion cancers originating in the lungs, thyroid and pancreas. Overall treatment with Selpercatinib was well tolerated. According to the investigators the anti-cancer responses to Selpercatinib have been durable. None of the responding patients has relapsed to date, with the longest-followed patient still on therapy 10 months since beginning treatment.
In a more recent analyses reported in September 2019 105 patients with advanced RET fusion-positive NSCLC who had received pretreatment with platinum-based chemotherapy and were subsequently treated with selpercatinib in the LIBRETTO-001 study, the overall response to treatment was 68%. Responses were durable, with a median duration of response of 20.3 months. Ninty-one percent of NSCLC patients with measurable brain metastases responded to treatment with selpercatinib.
The most common side effects are low white blood count, dry mouth, diarrhea, hypertension, fatigue, edema, decreased platelets, rash, and constipation.
RET in Thyroid Cancer
Selpercatinib is also currently available for treatment of Thyroid Cancer. RET fusions occur when a portion of the chromosome containing the RET gene breaks and rejoins with another piece of chromosome, creating a fusion protein capable of fueling cancer growth. RET alterations also occur in roughly 10-20% of papillary thyroid cancers (PTC) and the vast majority of medullary thyroid cancers (MTC). Up to half of all RET fusion-positive cancers metastasize to the brain.
Among patients with MTC the response to treatment was 73% in previously untreated patients and 69% in those receiving prior targeted therapies. In patients with previously treated papillary/anaplastic thyroid cancer, the response rate was 79%.
- Drilon A, Oxnard GR, Wirth L, et al. A phase 1/2 trial of LOXO-292 in patients with RET fusion-positive lung cancers. Presented at: IASLC 2019 World Conference on Lung Cancer hosted by the International Association for the Study of Lung Cancer; September 7-10, 2019; Barcelona, Spain. Abstract PL02.08.
- International Association for the Study of Lung Cancer. Registrational data from the LIBRETTO-1 trial demonstrate compelling and durable activity of selpercatinib (LOXO-292) in RET fusion-positive lung cancer. Published September 9, 2019. Accessed September 9, 2019.
- FDA approves selpercatinib for lung and thyroid cancers with RET gene mutations or fusions