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Efficacy of Selpercatinib in RET-Altered Thyroid Cancers
Lori J Wirth1, Eric Sherman1, Bruce Robinson1
1From Massachusetts General Hospital (L.J.W.) and Dana-Farber Cancer Institute (J. Lorch), Boston; Memorial Sloan Kettering Cancer Center, New York (E.S., A.D.); Royal North Shore Hospital, St. Leonards, NSW (B.R.), and Peter MacCallum Cancer Institute, Melbourne, VIC (B.S.) - both in Australia; University of California, San Francisco-Helen Diller Family Comprehensive Cancer Center, San Francisco (H.K.), David Geffen School of Medicine at UCLA, Los Angeles (J.W.G.), and Chao Family Comprehensive Cancer Center, University of California Irvine, Orange (V.W.Z.) - all in California; University of Michigan, Ann Arbor (F.W.), and START Midwest, Grand Rapids (N.L.) - both in Michigan; University of Pennsylvania, Philadelphia (M.B.); University of Chicago, Chicago (J.P.); Gustave Roussy, Villejuif (S.L.), Institut Bergonié, Bordeaux (Y.G.), Aix Marseille University, Centre National de la Recherche Scientifique, INSERM, Centre de Recherche en Cancérologie de Marseille, Assistance Publique-Hôpitaux de Marseille, Early Phase Cancer Trial Center CLIP2, Hospital La Timone, Marseille (F.B.), Centre Léon Bérard, Lyon (C.D.L.F.), and Hôpital Européen Georges-Pompidou, Faculté de Médecine Paris-Descartes, Paris (J.M.) - all in France; Mayo Clinic-Rochester, Rochester, MN (J.C.M.); Winship Cancer Institute of Emory University, Atlanta (T.K.O.); National Cancer Center Singapore, Singapore (D.S.W.T.); University of Bern, Bern, and Cantonal Hospital of Lucerne, Lucerne - both in Switzerland (O.G.); University of North Carolina-Chapel Hill, Chapel Hill (J.W.); University of Wisconsin-Carbone Cancer Center, Madison (M.E.B.); British Columbia Cancer Agency, Vancouver, Canada (J. Laskin); Oregon Health and Science University, Portland (M.H.T.); Universitätsklinikum Würzburg, Department of Internal Medicine I, Division of Endocrinology and Diabetology, Würzburg, Germany (M.K.); Sarah Cannon Research Institute-Tennessee Oncology, Nashville (T.M.B.); Johns Hopkins Kimmel Cancer Center, Washington, DC (B.L.); Fundación Jimenez Diaz, START-Madrid, Madrid (V.M.); Loxo Oncology, Stamford, CT (K.E., M.N., D.H., E.Y.Z., X.H., L.Y., J.K., S.M.R.); University of Texas M.D. Anderson Cancer Center, Houston (V.S., M.E.C.); and Ohio State University Comprehensive Cancer Center, Columbus (M.H.S.).
Background:
RET mutations occur in 70% of medullary thyroid cancers, and RET fusions occur rarely in other thyroid cancers. In patients with RET-altered thyroid cancers, the efficacy and safety of selective RET inhibition are unknown.
Methods:
We enrolled patients with RET-mutant medullary thyroid cancer with or without previous vandetanib or cabozantinib treatment, as well as those with previously treated RET fusion-positive thyroid cancer, in a phase 1-2 trial of selpercatinib. The primary end point was an objective response (a complete or partial response), as determined by an independent review committee. Secondary end points included the duration of response, progression-free survival, and safety.
Results:
In the first 55 consecutively enrolled patients with RET-mutant medullary thyroid cancer who had previously received vandetanib, cabozantinib, or both, the percentage who had a response was 69% (95% confidence interval [CI], 55 to 81), and 1-year progression-free survival was 82% (95% CI, 69 to 90). In 88 patients with RET-mutant medullary thyroid cancer who had not previously received vandetanib or cabozantinib, the percentage who had a response was 73% (95% CI, 62 to 82), and 1-year progression-free survival was 92% (95% CI, 82 to 97). In 19 patients with previously treated RET fusion-positive thyroid cancer, the percentage who had a response was 79% (95% CI, 54 to 94), and 1-year progression-free survival was 64% (95% CI, 37 to 82). The most common adverse events of grade 3 or higher were hypertension (in 21% of the patients), increased alanine aminotransferase level (in 11%), increased aspartate aminotransferase level (in 9%), hyponatremia (in 8%), and diarrhea (in 6%). Of all 531 patients treated, 12 (2%) discontinued selpercatinib owing to drug-related adverse events.
Conclusions:
In this phase 1-2 trial, selpercatinib showed durable efficacy with mainly low-grade toxic effects in patients with medullary thyroid cancer with and without previous vandetanib or cabozantinib treatment. (Funded by Loxo Oncology and others; LIBRETTO-001 ClinicalTrials.gov number, NCT03157128.).
Insights
Selpercatinib demonstrated significant efficacy in treating RET-altered thyroid cancers, including medullary thyroid cancer and RET fusion-positive types. The drug showed durable responses and manageable safety profiles in patients, regardless of prior treatment.
Area of Science:
- Oncology
- Molecular Biology
- Clinical Trials
Background:
- RET mutations are prevalent in medullary thyroid cancer (MTC) and RET fusions occur in other thyroid cancers.
- The efficacy and safety of selective RET inhibition in RET-altered thyroid cancers were previously unknown.
Purpose of the Study:
- To evaluate the efficacy and safety of selpercatinib, a selective RET inhibitor, in patients with RET-altered thyroid cancers.
- To assess response rates, duration of response, progression-free survival, and adverse events.
Main Methods:
- A phase 1-2 clinical trial (LIBRETTO-001) was conducted.
- Patients with RET-mutant MTC (with or without prior treatment) and previously treated RET fusion-positive thyroid cancer were enrolled.
- Objective response, duration of response, progression-free survival, and safety were assessed.
Main Results:
- High response rates were observed: 69% in previously treated MTC, 73% in treatment-naive MTC, and 79% in fusion-positive thyroid cancer.
- One-year progression-free survival rates were 82%, 92%, and 64%, respectively.
- Common grade 3+ adverse events included hypertension (21%) and elevated liver enzymes (11% and 9%).
Conclusions:
- Selpercatinib demonstrated durable efficacy in patients with RET-mutant MTC and RET fusion-positive thyroid cancer.
- The drug was generally well-tolerated, with mainly low-grade toxic effects.
- Selpercatinib represents a promising targeted therapy for RET-altered thyroid cancers.
