Roblitinib

Deregulation of FGF19-FGFR4 signaling is found in several cancers, including hepatocellular carcinoma (HCC), nominating it for therapeutic targeting. FGF401 is a potent, selective FGFR4 inhibitor with antitumor activity in preclinical models. This study was designed to determine the recommended phase 2 dose (RP2D), characterize PK/PD, and evaluate the safety and efficacy of FGF401 alone and combined with the anti-PD-1 antibody, spartalizumab.

Patients with HCC or other FGFR4/KLB expressing tumors were enrolled. Dose-escalation was guided by a Bayesian model. Phase 2 dose-expansion enrolled patients with HCC from Asian countries (group1), non-Asian countries (group2), and patients with other solid tumors expressing FGFR4 and KLB (group3). FGF401 and spartalizumab combination was evaluated in patients with HCC.

Seventy-four patients were treated in the phase I with single-agent FGF401 at 50 to 150 mg. FGF401 displayed favorable PK characteristics and no food effect when dosed with low-fat meals. The RP2D was established as 120 mg qd. Six of 70 patients experienced grade 3 dose-limiting toxicities: increase in transaminases (n = 4) or blood bilirubin (n = 2). In phase 2, 30 patients in group 1, 36 in group 2, and 20 in group 3 received FGF401. In total, 8 patients experienced objective responses (1 CR, 7 PR; 4 each in phase I and phase II, respectively). Frequent adverse events (AEs) were diarrhea (73.8%), increased AST (47.5%), and ALT (43.8%). Increase in levels of C4, total bile acid, and circulating FGF19, confirmed effective FGFR4 inhibition.Twelve patients received FGF401 plus spartalizumab. RP2D was established as FGF401 120 mg qd and spartalizumab 300 mg Q3W; 2 patients reported PR.

At biologically active doses, FGF401 alone or combined with spartalizumab was safe in patients with FGFR4/KLB-positive tumors including HCC. Preliminary clinical efficacy was observed. Further clinical evaluation of FGF401 using a refined biomarker strategy is warranted.

NCT02325739.

Rhabdomyosarcoma (RMS) is a paediatric cancer driven either by fusion proteins (e.g., PAX3-FOXO1) or by mutations in key signalling molecules (e.g., RAS or FGFR4). Despite the latter providing opportunities for precision medicine approaches in RMS, there are currently no such treatments implemented in the clinic.

We evaluated biologic properties and targeting strategies for the FGFR4 V550L activating mutation in RMS559 cells, which have a high allelic fraction of this mutation and are oncogenically dependent on FGFR4 signalling. Signalling and trafficking of FGFR4 V550L were characterised by confocal microscopy and proteomics. Drug effects were determined by live-cell imaging, MTS assay, and in a mouse model.

Among recently developed FGFR4-specific inhibitors, FGF401 inhibited FGFR4 V550L-dependent signalling and cell proliferation at low nanomolar concentrations. Two other FGFR4 inhibitors, BLU9931 and H3B6527, lacked potent activity against FGFR4 V550L. Alternate targeting strategies were identified by RMS559 phosphoproteomic analyses, demonstrating that RAS/MAPK and PI3K/AKT are essential druggable pathways downstream of FGFR4 V550L. Furthermore, we found that FGFR4 V550L is HSP90-dependent, and HSP90 inhibitors efficiently impeded RMS559 proliferation. In a RMS559 mouse xenograft model, the pan-FGFR inhibitor, LY2874455, did not efficiently inhibit growth, whereas FGF401 potently abrogated growth.

Our results pave the way for precision medicine approaches against FGFR4 V550L-driven RMS.