Phase 1 dose escalation study of the MDM2 inhibitor milademetan as monotherapy and in combination with azacitidine in patients with myeloid malignancies.

BACKGROUND: Mouse double minute-2 homolog (MDM2) plays a key role in downregulating p53 activity in hematologic malignancies, and its overexpression is associated with poor outcomes. METHODS: This phase 1 study assessed the safety and efficacy of different dosing regimens of the MDM2 inhibitor milademetan as monotherapy and in combination with azacitidine (AZA) in patients with relapsed or refractory acute myeloid leukemia or high-risk myelodysplastic syndromes. RESULTS: Seventy-four patients (monotherapy, n = 57; milademetan-AZA combination, n = 17) were treated. The maximum tolerated dose of milademetan was 160 mg once daily given for the first 14-21 days of 28-day cycles as monotherapy and on Days 5-14 in combination with AZA. Dose-limiting toxicities were gastrointestinal, fatigue, or renal/electrolyte abnormalities. Treatment-emergent adverse events related to milademetan occurred in 82.5% and 64.7% of participants in the monotherapy and AZA combination arms, respectively. Two participants (4.2%) in the monotherapy arm achieved complete remission (CR), and 1 (2.1%) achieved CR with incomplete blood count recovery (CRi). Two participants (13.3%) achieved CRi in the combination arm. New TP53 mutations, detected only during milademetan monotherapy, were found pre-existing below standard detection frequency by droplet digital polymerase chain reaction. INTERPRETATION: Milademetan was relatively well tolerated in this population; however, despite signals of activity, clinical efficacy was minimal.

The multi-kinase inhibitor CG-806 exerts anti-cancer activity against acute myeloid leukemia by co-targeting FLT3, BTK, and aurora kinases.

Despite the development of several Fms-like tyrosine kinase 3 (FLT3) inhibitors that have improved outcomes in patients with FLT3-mutant acute myeloid leukemia (AML), drug resistance is frequently observed, which may be associated with the activation of additional pro-survival pathways, such as those regulated by BTK, aurora kinases (AuroK), and potentially others, in addition to acquired tyrosine kinase domain (TKD) mutations of FLT3 gene. FLT3 may not always be a driver mutation. We evaluated the anti-leukemia efficacy of the novel multi-kinase inhibitor CG-806, which targets FLT3 and other kinases, to circumvent drug resistance and target FLT3 wild-type (WT) cells. The anti-leukemia activity of CG-806 was investigated by measuring apoptosis induction and analyzing the cell cycle using flow cytometry in vitro. CG-806 demonstrated superior anti-leukemia efficacy compared to commercially available FLT3 inhibitors, both in vitro and in vivo, regardless of FLT3 mutational status. The mechanism of action of CG-806 may involve its broad inhibitory profile against FLT3, BTK, and AuroK. In FLT3 mutant cells, CG-806 induced G1 phase blockage, whereas in FLT3 WT cells, it resulted in G2/M phase arrest. Targeting FLT3 and Bcl-2 and/or Mcl-1 simultaneously results in a synergistic pro-apoptotic effect in FLT3 mutant leukemia cells. The results of this study suggest that CG-806 is a promising multi-kinase inhibitor with anti-leukemic efficacy regardless of FLT3 mutational status. A phase 1 clinical trial of CG-806 for the treatment of AML has been initiated (NCT04477291).Key pointsThe multi-kinase inhibitor CG-806 exerts superior anti-leukemic activity in AML, regardless of its FLT3 status.CG-806 triggered G1 arrest in FLT3 mutated cells and G2/M arrest in FLT3 WT cells through the suppression of FLT3/BTK and aurora kinases.Concomitantly targeting FLT3 and Bcl-2 and/or Mcl-1 exerted synergistic pro-apoptotic effects on both FLT3 WT and mutated AML cells.

Age-specific induction of mutant p53 drives clonal hematopoiesis and acute myeloid leukemia in adult mice.

The investigation of the mechanisms behind p53 mutations in acute myeloid leukemia (AML) has been limited by the lack of suitable mouse models, which historically have resulted in lymphoma rather than leukemia. This study introduces two new AML mouse models. One model induces mutant p53 and Mdm2 haploinsufficiency in early development, showing the role of Mdm2 in myeloid-biased hematopoiesis and AML predisposition, independent of p53. The second model mimics clonal hematopoiesis by inducing mutant p53 in adult hematopoietic stem cells, demonstrating that the timing of p53 mutation determines AML vs. lymphoma development. In this context, age-related changes in hematopoietic stem cells (HSCs) collaborate with mutant p53 to predispose toward myeloid transformation rather than lymphoma development. Our study unveils new insights into the cooperative impact of HSC age, Trp53 mutations, and Mdm2 haploinsufficiency on clonal hematopoiesis and the development of myeloid malignancies.

Outcome of 3q26.2/MECOM rearrangements in chronic myeloid leukemia.

STUDY AIMS: To evaluate the outcomes of patients with 3q26.2/MECOM-rearranged chronic myeloid leukemia (CML). METHODS: We reviewed consecutive adult patients with 3q26.2/MECOM-rearranged CML between January 1, 1998 and February 16, 2023. Rearrangements of 3q26.2/MECOM were confirmed by conventional cytogenetics, and fluorescence in situ hybridization starting in 2015. RESULTS: We identified 55 patients with MECOM-rearranged CML, including 23 in chronic phase (CP) or accelerated phase (AP) and 32 in blast phase (BP). Nine patients (16%) achieved a major cytogenetic response (MCyR) or deeper. At a median follow-up of 89 months, median survival was 14 months. The 5-year survival rate was 19% overall, 23% in CML-CP/AP, and 15% in CML-BP. In the 6-month landmark analysis, the 5-year survival rate was 41% for allogeneic stem cell transplantation (allo-SCT) recipients versus 17% for non-recipients (P = 0.050). Multivariate analysis showed that the percentage of marrow blasts and achievement of MCyR or deeper could predict survival. CONCLUSION: Outcomes of 3q26.2/MECOM-rearranged CML are poor despite the availability of multiple BCR::ABL1 tyrosine kinase inhibitors (TKIs). Third-generation TKIs in combination with novel agents and possible allo-SCT could be considered given the poor outcomes and resistance to second-generation TKIs.

Combination of dasatinib and venetoclax in newly diagnosed chronic phase chronic myeloid leukemia.

BACKGROUND: The dual inhibition of the BCR::ABL1 tyrosine kinase and BCL-2 could potentially deepen the response rates of chronic myeloid leukemia in chronic phase (CML-CP). This study evaluated the safety and efficacy of the combination of dasatinib and venetoclax. METHODS: In this phase 2 trial, patients with CML-CP or accelerated phase (clonal evolution) received dasatinib 50 mg/day for three courses; venetoclax was added in course 4 for 3 years. The initial venetoclax dose was 200 mg/day continuously but reduced later to 200 mg/day for 14 days, and to 100 mg/day for 7 days per course once a molecular response (MR)4.5 was achieved. After 3 years of combination, patients were maintained on single-agent dasatinib. The primary end point was the rate of major molecular response (MMR) by 12 months of combination. RESULTS: Sixty-five patients were treated. Their median age was 46 years (range, 23-73). By 12 months of combination, the MMR, MR4, and MR4.5 rates were 86%, 53%, and 45%, respectively. After a median follow-up of 42 months, the 4-year event-free and overall survival rates were 96% and 100%, respectively. Outcomes with the combination were comparable to historical outcomes with single-agent dasatinib (cumulative 12-months MMR rate of 79% with both strategies). The incidence of grade 3-4 neutropenia was 22% with the combination and 11% with single-agent dasatinib (p < .001). CONCLUSIONS: Treatment with dasatinib and venetoclax was safe and effective in CML-CP. The cumulative response rates with the combination were similar to those with single-agent dasatinib. Further follow-up is needed to evaluate the rates of durable deep molecular response and treatment-free remission.

Venetoclax and Cobimetinib in Relapsed/Refractory AML: A Phase 1b Trial.

BACKGROUND: Therapies for relapsed/refractory acute myeloid leukemia remain limited and outcomes poor, especially amongst patients who are ineligible for cytotoxic chemotherapy or targeted therapies. PATIENTS AND METHODS: This phase 1b trial evaluated venetoclax, a B-cell lymphoma-2 (BCL-2) inhibitor, plus cobimetinib, a MEK1/2 inhibitor, in patients with relapsed/refractory acute myeloid leukemia, ineligible for cytotoxic chemotherapy. Two-dimensional dose-escalation was performed for venetoclax dosed daily, and for cobimetinib dosed on days 1-21 of each 28-day cycle. RESULTS: Thirty patients (median [range] age: 71.5 years [60-84]) received venetoclax-cobimetinib. The most common adverse events (AEs; in ≥40.0% of patients) were diarrhea (80.0%), nausea (60.0%), vomiting (40.0%), febrile neutropenia (40.0%), and fatigue (40.0%). Overall, 66.7% and 23.3% of patients experienced AEs leading to dose modification/interruption or treatment withdrawal, respectively. The composite complete remission (CRc) rate (complete remission [CR] + CR with incomplete blood count recovery + CR with incomplete platelet recovery) was 15.6%; antileukemic response rate (CRc + morphologic leukemia-free state/partial remission) was 18.8%. For the recommended phase 2 dose (venetoclax: 600 mg; cobimetinib: 40 mg), CRc and antileukemic response rates were both 12.5%. Failure to achieve an antileukemic response was associated with elevated baseline phosphorylated ERK and MCL-1 levels, but not BCL-xL. Baseline mutations in ≥1 signaling gene or TP53 were noted in nonresponders and emerged on treatment. Pharmacodynamic biomarkers revealed inconsistent, transient inhibition of the mitogen-activated protein kinase (MAPK) pathway. CONCLUSION: Venetoclax-cobimetinib showed limited preliminary efficacy similar to single-agent venetoclax, but with added toxicity. Our findings will inform future trials of BCL-2/MAPK pathway inhibitor combinations.

Mitochondrial regulation of GPX4 inhibition-mediated ferroptosis in acute myeloid leukemia.

Resistance to apoptosis in acute myeloid leukemia (AML) cells causes refractory or relapsed disease, associated with dismal clinical outcomes. Ferroptosis, a mode of non-apoptotic cell death triggered by iron-dependent lipid peroxidation, has been investigated as potential therapeutic modality against therapy-resistant cancers, but our knowledge of its role in AML is limited. We investigated ferroptosis in AML cells and identified its mitochondrial regulation as a therapeutic vulnerability. GPX4 knockdown induced ferroptosis in AML cells, accompanied with characteristic mitochondrial lipid peroxidation, exerting anti-AML effects in vitro and in vivo. Electron transport chains (ETC) are primary sources of coenzyme Q10 (CoQ) recycling for its function of anti-lipid peroxidation in mitochondria. We found that the mitochondria-specific CoQ potently inhibited GPX4 inhibition-mediated ferroptosis, suggesting that mitochondrial lipid redox regulates ferroptosis in AML cells. Consistently, Rho0 cells, which lack functional ETC, were more sensitive to GPX4 inhibition-mediated mitochondrial lipid peroxidation and ferroptosis than control cells. Furthermore, degradation of ETC through hyperactivation of a mitochondrial protease, caseinolytic protease P (ClpP), synergistically enhanced the anti-AML effects of GPX4 inhibition. Collectively, our findings indicate that in AML cells, GPX4 inhibition induces ferroptosis, which is regulated by mitochondrial lipid redox and ETC.