milademetan (RAIN-32)

P2, N=1, Terminated, Institut Curie | N=48 --> 1 | Trial completion date: Dec 2026 --> Nov 2023 | Active, not recruiting --> Terminated | Trial primary completion date: Aug 2025 --> Nov 2023; Financial partner providing study drug could no longer support the trial

P2, N=48, Active, not recruiting, Institut Curie | Recruiting --> Active, not recruiting

No abstract available

Avelumab therapy has shown promising results in Merkel cell polyomavirus (MCPyV)-negative MCC patients with TMB-H, while pembrolizumab therapy has shown better response in patients with low TMB. A study evaluating neoadjuvant nivolumab therapy found no significant difference in treatment response between the tumor etiologies and TMB levels. In addition to ICI therapy, other treatments that induce apoptosis, such as milademetan, have demonstrated positive responses in MCPyV-positive MCC, with few somatic mutations and wild-type TP53. This review summarizes current knowledge and discusses emerging and potentially predictive biomarkers for MCC therapy with ICI.

P2, N=40, Terminated, Rain Oncology Inc | N=65 --> 40 | Trial completion date: Aug 2024 --> Oct 2023 | Active, not recruiting --> Terminated | Trial primary completion date: Aug 2024 --> Oct 2023; Sponsor Decision

P2, N=48, Recruiting, Institut Curie | Not yet recruiting --> Recruiting

No abstract available

Acquired TP53 mutations were detected in sequential liquid biopsies as a novel exploratory resistance mechanism to milademetan. These results suggest that milademetan could be a potential therapeutic strategy for intimal sarcoma.

P2, N=65, Active, not recruiting, Rain Oncology Inc | Recruiting --> Active, not recruiting

Further evaluation of milademetan is warranted in populations that may benefit from MDM2 inhibition. Table: LBA89 Study findings Efficacy population Milademetan (n=86) Trabectedin (n=89) Median PFS by BICR, m 3.6 2.2 HR=0.89 (95% CI 0.61–1.29; p=0.53) Median PFS by investigator, m 3.7 2.1 HR=0.80 (95% CI 0.55–1.15; p=0.22) Median OSa, m 9.5 10.2 HR=1.27 (95% CI 0.80–2.04; p=0.31) ORR, n (%) 4 (4.7) 3 (3.4) p=0.67 DCR, n (%) 29 (33.7) 24 (27.0) p=0.33 Safety population n=86 n=79 Most common milademetan TEAEs, %NauseaThrombocytopeniaAnemiaVomiting 70.961.644.244.2 58.225.336.719.0 Most common grade 3/4 milademetan TEAEs, %ThrombocytopeniaNeutropeniaAnemia 39.525.618.6 13.926.619.0 TEAEs – fatal/grade 5, % 0 6.3 TEAEs leading to dose reductions, % 44.2 29.1 TEAEs leading to discontinuations, % 11.6 19.0

P2, N=48, Not yet recruiting, Institut Curie

The combination of milademetan, LDAC±venetoclax led to only modest responses with recognizable gastrointestinal toxicity. Treatment-induced reduction of MCL1 and YTHDF2 in an immune-rich milieu correlate with treatment response.

P1/2, N=16, Terminated, M.D. Anderson Cancer Center | Completed --> Terminated; This study was terminated early due to lack of adequate response, and did not move to the Phase II portion of the study

Molecular-guided precision medicine holds a bright future in bringing more active treatments for advanced sarcoma patients.

Combined MDM2/MEK inhibition demonstrates efficacy across multiple patient-derived LUAD models harboring MDM2amp and concurrent oncogenic drivers. This combination, potentially applicable to LUADs with a wide variety of oncogenic driver mutations and kinase fusions activating the MAPK pathway, has evident clinical implications and will be investigated as part of a planned phase 1/2 clinical trial.

CDKN2A loss and amplified TWIST1 could be associated with the anti-tumor activity of milademetan in patients with amplified MDM2 intimal sarcoma. Acquired TP53 mutations were detected in sequential liquid biopsies as loss-of-function mutations, and these TP53 mutations might compromise the anti-tumor activity. Clinical trial information: JMA-IIA00402.

The small molecule MDM2 inhibitor milademetan (mila) caused growth inhibition as a single-agent in MDM2amp patient-derived cell lines with concurrent kinase alterations including ECLC5-GLx (MDM2amp/TRIM33::RET/TP53 wildtype (WT)) and LUAD12c (MDM2amp/METex14/KRASG12S/TP53 WT)...At 48 hours, ERK phosphorylation was suppressed by concurrent mila and MEK inhibition using trametinib (tram). In contrast, ERK phosphorylation was not suppressed by concurrent mila and KIF5B::RET inhibition using selpercatinib (in ECLC5-GLx) or MET inhibition using capmatinib (in LUAD12c)...These results suggest that combined MDM2/MEK inhibition is effective in patient-derived LUAD models harboring MDM2amp. This combination, potentially applicable to LUADs with a wide variety of oncogenic driver mutations and kinase fusions will be investigated as part of a phase 1/2 clinical trial.

Preliminary investigation into this effect suggests synergism in combination with milademetan treatment, with the MDM2-p53 inhibition driven increase in MDM2 levels being abolished upon cotreatment of ONC201 and milademetan. Further exploration of this combination is underway, and may serve as a novel translatable therapeutic approach, particularly in combination with checkpoint blockade.

In contrast, ERK phosphorylation was not suppressed by concurrent milademetan and KIF5B::RET inhibition using selpercatinib (in ECLC5-GLx), MET inhibition using capmatinib (in LUAD12c), or KRASG12C inhibition using sotorasib (in SW1573)...In vivo, milademetan+trametinib was more effective than milademetan or trametinib alone in ECLC5-GLx (p<0.0001 and p<0.0001, respectively), LX-285 (EGFRex19del/MDM2amp) (p<0.0001 and p<0.0001, respectively), L-13BS1 (model resistant to capmatinib) (METex14/MDM2amp) (p<0.05 and p<0.0001, respectively)...CONCLUSION Combined MDM2/MEK inhibition is effective in patient-derived LUAD models harboring MDM2amp. This combination, potentially applicable to LUADs with a wide variety of oncogenic driver mutations and kinase fusions will be investigated as part of a phase 1/2 clinical trial.

Similar results were obtained for the other two MDM2 inhibitors, AMG232 and DS-3032b, and a BCL2 inhibitor, venetoclax...Furthermore, overexpressing GATA2 conferred Idasanutlin resistance at high concentrations. Finally, we observed that combining a FLT3/IRAK dual inhibitor, pacritinib, or an IRAK1 /IL-1 receptor antagonist, anakinra, partially rescued IL-1α and IL-1β mediated drug resistance of MDM2 inhibitors. As such, we uncovered the role of leukemia-associated monocyte in driving intrinsic and extrinsic MDM2 inhibitor resistance and the potential underlying mechanisms.

We investigated the combination of the HMA azacitidine (AZA) with DS-3032b and DS-5272, novel antagonists of the TP53 negative regulator MDM2, in cellular and animal models of MDS and CMML. RNA-Seq analysis in mouse bone marrow hematopoietic stem and progenitors indicated that DS-5272 and AZA combination caused down-regulation of leukemia stem cell marker genes and activation of pathways of TP53 function and stability. These findings demonstrate that combining an MDM2 antagonist with AZA has potential to improve AZA treatment in TP53 wildtype MDS and CMML.

The combination of milademetan and trametinib demonstrated synergy in vitro and combinatorial superiority in vivo. These data support the exploration of combination of milademetan and MAPK inhibition in patients whose tumors harbor selected genetic alterations, including MDM2 amplification, CDKN2A loss or WT TP53.

Molecular docking indicated that DS-3032B antagonist binds to the same region of the p53 binding site in the MDM2 with high affinity and stability, and this suggests therapeutic efficiency.

Milademetan showed a dose-dependent inhibition of tumor growth in MKL-1 xenograft and patient-derived xenograft models. Here, along with preclinical data for the efficacy of milademetan in WT p53 MCC tumors, we report several in vitro and in vivo models useful for future MCC studies.

Conclusion The combination of milademetan with LDAC ± venetoclax was reasonably well tolerated but showed only minimal clinical responses at all 3 dose levels in a heavily pre-treated AML population. Further studies are needed to decipher the most appropriate combination regimen and pt population to benefit from milademetan.

Enrollment of 65 patients is planned to ensure that 57 patients have centrally confirmed TP53 WT and MDM2 copy number ≥ 12. The trial opened in November 2021 and is actively enrolling patients.

P1/2, N=21, Completed, M.D. Anderson Cancer Center | Active, not recruiting --> Completed | Trial completion date: Dec 2023 --> Apr 2022 | Trial primary completion date: Dec 2022 --> Apr 2022

P1/2, N=21, Active, not recruiting, M.D. Anderson Cancer Center | Recruiting --> Active, not recruiting | N=58 --> 21

Pharmacological inhibition of MDM2 using three different compounds (RG7388-idasanutlin, RAIN-32 and MI-733) significantly impaired tumor growth in GATA3-deficient models in vitro, in vivo and in patient-derived organoid/ xenograft (PDO/ PDX) harboring GATA3 somatic mutation. Our results present MDM2 as a novel therapeutic target in the substantial cohort of ER-positive, GATA3-mutant breast cancer patients. With MDM2 inhibitors widely available, our findings can be rapidly translated into clinical trials to evaluate in-patient efficacy.

Enrollment of 65 patients is planned to ensure that 57 patients have centrally confirmed TP53 WT and MDM2 copy number ≥12. The trial opened in November 2021 and is actively enrolling patients.

P2, N=65, Recruiting, Rain Therapeutics Inc. | Not yet recruiting --> Recruiting

Further validation is needed in a larger cohort of patients. Such approaches could be utilized in clinical-trial settings to predict therapy response with targeted agents and inform clinical decision-making.

Clinical grade MDM2 and XPO1 inhibitors milademetan (mil) and selinexor (sel) significantly reduced leukemia burden and prolonged survival in the xenograft model injected with MV4;11 VR cells...In a clinical trial of Idasanutlin + Venetoclax we observed over 45% response rates in relapsed/refractory AML patients (Daver, ASH 2020)...Next, we treated NSG mice injected with PDX AML cells with FLT3-ITD, GATA2 and NRAS mutations obtained from a patient who relapsed after ven/decitabine treatment...In conclusion, the concomitant inhibition of MDM2, XPO1 and BCL-2 was feasible and exerted dramatic and sustained anti-leukemia activity in ven/HMA resistant AML cell in vitro and in vivo. Milademetan (RAIN-32) is currently being developed by Rain Therapeutics.

P1/2, N=58, Recruiting, M.D. Anderson Cancer Center | Trial completion date: May 2022 --> Dec 2023 | Trial primary completion date: May 2021 --> Dec 2022

No abstract available

P2, N=65, Not yet recruiting, Rain Therapeutics Inc.

A clinical DDI study of milademetan (NCT03614455) showed that concomitant administration of single-dose milademetan with the strong CYP3A inhibitor itraconazole or posaconazole increased milademetan mean AUC by 2.15-fold (90% CI, 1.98-2.34) and 2.49-fold (90% CI, 2.26-2.74), respectively, supporting that the milademetan dose should be reduced by 50% when concomitantly administered with strong CYP3A inhibitors...The PBPK model predicted an increase in milademetan exposure of 1.72-fold (90% CI, 1.69-1.76) with fluconazole, 1.91-fold (90% CI, 1.83-1.99) with erythromycin, and 2.02-fold (90% CI, 1.93-2.11) with verapamil. In addition, it estimated that milademetan's original dose (160 mg once daily) could be resumed from its half-reduced dose 3 days after discontinuation of concomitant strong CYP3A inhibitors. The established PBPK model of milademetan was qualified and considered to be robust enough to support continued development of milademetan.

P1, N=74, Terminated, Daiichi Sankyo, Inc. | N=200 --> 74 | Trial completion date: Apr 2022 --> Aug 2020 | Active, not recruiting --> Terminated | Trial primary completion date: Jul 2021 --> Aug 2020

Further investigation revealed that nine genes (AURKB, HDAC2, PLK1, CENPA, CHEK1, CHEK2, RB1, CCNA2, and MDM2) in coordination with E:C fusion were found to be common denominators in three or more of these pathways, thereby making them promising gene biomarkers for target therapy. Among the 21 putative actionable drugs inferred by drug-target network analysis, palbociclib, alpelisib, ribociclib, dexamethasone, checkpoint kinase inhibitor AXD 7762, irinotecan, milademetan tosylate, R05045337, cisplatin, prexasertib, and olaparib were considered promising drug candidates targeting genes involved in at least two E:C fusion-related pathways.