According to the topline results, a total of 54% of patients given the treatment saw their tumors shrink compared to just 3.2% in the placebo group, hitting the primary endpoint of the trial.
TGCT is a rare condition mainly caused by an overexpression of the protein colony stimulating factor-1 receptor (CSF-1R), which drives the proliferation of a range of cells such as microglial cells and macrophages. This leads to joint pain, stiffness and potentially irreversible damage to joints and bones.
Surgery is the main approach for treating TGCT but can be difficult to carry out in some patients, while the only systemic therapy approved by the U.S. Food and Drug Administration – Daiichi Sankyo’s CSF-1R blocker pexidartinib (Turalio) – which needs to be taken twice daily and can show side effects such as hepatotoxicity.
“Based on these new data from the MANEUVER study, together with once-daily oral administration that may promote long-term adherence and pimicotinib’s selective inhibition of CSF-1R, this investigational medicine has the potential to establish a new treatment paradigm for patients with TGCT,” said Niu Xiaohui, study investigator and director of the Bone and Soft Tissue Tumour Diagnosis and Research Centre at Beijing Jishuitan Hospital, in a public statement.
The randomized, double-blind, placebo-controlled study tested the benefits of 50 mg pimicotinib daily against a placebo in 94 patients with TGCT in Europe, China and North America who haven’t received previous treatments blocking CSF-1R. The pimicotinib group also saw significant improvements in secondary endpoints such as stiffness and pain, and the drug was well-tolerated.
Abbisko licensed the commercial rights for pimicotinib in all indications in Chinese mainland, Hong Kong, Macau, and Taiwan to Merck KGaA in a deal worth $70 million upfront in 2023. The Chinese player is also aiming to develop the compound for the treatment of solid tumors, chronic graft-versus-host disease and advanced pancreatic cancer.
Pexidartinib (Turalio) was first approved in the U.S. in 2019, based on achieving an overall response rate (ORR) of 38% in phase 3 data. Another advanced contender is Deciphera’s vimseltinib, which hit an ORR of 40% in a phase 3 trial for the treatment of TGCT last year.
On the other hand, CSF-1R blockers have struggled to perform in clinical trials for the treatment of other tumor types, which may be due to the heterogeneity of cancer in general.
