Treatment with TP-0184 or in combination with BCL2 inhibitor, venetoclax dramatically inhibited leukemia growth in FLT3-mutated AML cell lines and patient-derived xenograft models in a dose-dependent manner. These findings suggest that ACVR1 is a novel biomarker and plays a role in AML resistance to FLT3 inhibitors and that FLT3/ACVR1 dual inhibitor TP-0184 is a novel potential therapeutic tool for AML with FLT3 mutations.

We also measured ACVR1 expression using qRT-PCR in FLT3-mutant AML cell lines (molm-13, molm-14, and MV4-11) treated with different doses of FLT3i (gilteritinib or midostaurin), as well as in peripheral blood mononuclear cells isolated from patients with FLT3-mutant AML treated with FLT3i...Interestingly,TP-0184 with venetoclax or cytarabine showed a synergistic effect in FLT3-mutant cells (combination index 0.01; p<0.01)... Our data indicate that ACVR1 causes resistance to FLT3 inhibitors. TP-0184, a dual inhibitor, targets mutant FLT3 and ACVR1 in AML cell lines. TP-0184 sensitizes AML cells with chemotherapy and venetoclax and inhibits AML growth in vivo.

Our data indicate that ALK2 is a prognostic marker in FLT3-mutated AML. TP-0184 inhibits cell proliferation by inhibiting FLT3 downstream signaling pathways in AML cells. Kinase assays confirmed that TP-0184 is a highly specific FLT3-ALK2 dual inhibitor. TP-0184 inhibits AML growth in FLT3-mutated PDX and xenograft models.

Preliminary data suggest that TP-0184 is tolerated as monotherapy at doses up to 125 mg QW; MTD was not reached. A study in pts with myelodysplastic syndromes is ongoing.

In phase 2, the efficacy of TP-0184 at the RP2D will be monitored using Bayesian posterior probability to optimize enrollment with Bayesian stopping rules. Bayesian monitoring of responses will be started after the first 10 enrolled patients are evaluable for efficacy.

Interestingly, TP-0184 plus chemotherapy showed a synergistic effect only in FLT3-ITD cell lines, whereas TP-0184 plus the BCL2 inhibitor, venetoclax was synergistic in both FLT3-ITD and FLT3-WT cell lines. Our data indicate that ALK2 is a prognostic marker for AML patients with FLT3-ITD mutations. TP-0184 significantly inhibits cell proliferation by inhibiting signaling pathways downstream of FLT3, including serine biosynthesis, in AML cells. Kinase assays confirmed that TP-0184 is a highly specific FLT3 inhibitor as well as an ALK2 inhibitor.