A new 3-case report demonstrates the potential of avapritinib to facilitate the bridge to allogeneic hematopoietic cell transplantation (allo-HCT) in patients with advanced systemic mastocytosis (SM).
The patients in the case reports, published in Translational Medicine, all achieved complete remission, and 2 of the patients had clonal evolution of the associated hematological neoplasm (AHN) and developed acute myeloid leukemia.
“SM-AHN patients are often associated with a myeloid neoplasm, including myeloproliferative neoplasm, chronic myelomonocytic leukaemia, and myelodysplasia, which frequently impacts on clinical outcomes,” the authors wrote. “We report three cases of AdvSM patients with AHN receiving avapritinib, two on the EXPLORER study and one on a named patient basis, who achieved CR of SM and were successfully bridged to allo-HCT.”
The cases included a 45-year-old woman treated with 60 mg of avapritinib once daily, which was increased to 100 mg from cycle 10 onward. Within 6 months, she had a significant clinical response and she achieved complete remission at 18 months. She later underwent allo-HCT and currently remains in complete remission with stable SM.
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The next case was a 64-year-old man who was treated with 200 mg of avapritinib once daily, followed by 100 mg daily, achieving complete remission by 12 months. He later developed acute myeloid leukemia, and following allo-HCT, he relapsed and ultimately died.
The third case was a 57-year-old man who was treated with 50 mg of avapritinib daily titrated by platelet count, achieving complete remission by 6 months, followed by allo-HCT. He developed some complications but remains in complete remission at this time.
The authors conclude that avapritinib shows promise in facilitating the bridge to allo-HCT, currently the only potentially curative option for patients with SM. However, they caution that many questions remain about the optimal conditioning and monitoring regimen needed to achieve the best outcomes possible.
Sriskandarajah P, McLornan DP, Oni C, et al. Advanced systemic mastocytosis with associated haematological neoplasm: treatment with avapritinib can facilitate successful bridge to allogeneic haematopoietic cell transplant. Transl Med. Published online June 13, 2023. doi:10.1016/j.retram.2023.103398