Phase I/Ib, open-label, multicenter, dose-escalation study of the anti-TGF-ß monoclonal antibody, NIS793, in combination with spartalizumab in adult patients with advanced tumors.

BACKGROUND: NIS793 is a human IgG2 monoclonal antibody that binds to transforming growth factor beta (TGF-ß). This first-in-human study investigated NIS793 plus spartalizumab treatment in patients with advanced solid tumors. METHODS: Patients received NIS793 (0.3-1 mg/kg every 3 weeks (Q3W)) monotherapy; following evaluation of two dose levels, dose escalation continued with NIS793 plus spartalizumab (NIS793 0.3-30 mg/kg Q3W and spartalizumab 300 mg Q3W or NIS793 20-30 mg/kg every 2 weeks [Q2W] and spartalizumab 400 mg every 4 weeks (Q4W)). In dose expansion, patients with non-small cell lung cancer (NSCLC) resistant to prior anti-programmed death ligand 1 or patients with microsatellite stable colorectal cancer (MSS-CRC) were treated at the recommended dose for expansion (RDE). RESULTS: Sixty patients were treated in dose escalation, 11 with NIS793 monotherapy and 49 with NIS793 plus spartalizumab, and 60 patients were treated in dose expansion (MSS-CRC: n=40; NSCLC: n=20). No dose-limiting toxicities were observed. The RDE was established as NIS793 30 mg/kg (2100 mg) and spartalizumab 300 mg Q3W. Overall 54 (49.5%) patients experienced ≥1 treatment-related adverse event, most commonly rash (n=16; 13.3%), pruritus (n=10; 8.3%), and fatigue (n=9; 7.5%). Three partial responses were reported: one in renal cell carcinoma (NIS793 30 mg/kg Q2W plus spartalizumab 400 mg Q4W), and two in the MSS-CRC expansion cohort. Biomarker data showed evidence of target engagement through increased TGF-ß/NIS793 complexes and depleted active TGF-ß in peripheral blood. Gene expression analyses in tumor biopsies demonstrated decreased TGF-ß target genes and signatures and increased immune signatures. CONCLUSIONS: In patients with advanced solid tumors, proof of mechanism of NIS793 is supported by evidence of target engagement and TGF-ß pathway inhibition. TRIAL REGISTRATION NUMBER: NCT02947165.

A First-in-Human, Phase I, Multicenter, Open-Label, Dose-Escalation Study of PCA062: An Antibody-Drug Conjugate Targeting P-Cadherin, in Patients With Solid Tumors.

This first-in-human (FIH), phase I, multicenter, open-label study was conducted to characterize the safety, tolerability, pharmacokinetics, and preliminary efficacy, and to establish the MTD/recommended dose for expansion (RDE) of PCA062 in patients with solid tumors. Adult patients with any solid tumor type and having a documented P-cadherin-positive tumor were enrolled; exceptions to P-cadherin positivity requirement were head and neck squamous cell carcinomas (HNSCC) and esophageal squamous cell carcinoma (ESCC). Dose escalation was guided by an adaptive Bayesian logistic regression model with escalation with overdose control to determine the MTD/RDE. Forty-seven patients were treated at 10 different dose levels of PCA062, ranging from 0.4 to 5.0 mg/kg every 2 weeks administered as a 1-hour intravenous infusion. All enrolled patients discontinued the treatment; primary reason for discontinuation was progressive disease (78.7%). All 47 patients experienced at least one AE, of which 32 patients had a grade ≥3 AE and 37 patients experienced AEs suspected to be study drug related. The MTD of PCA062 was 3.6 mg/kg every 2 weeks and thrombocytopenia was reported as a DLT that was attributed to the known toxicities of the DM1 payload with no P-cadherin-related toxicities. Pharmacokinetics was proportional, and no patients developed antidrug antibodies, suggesting adequate exposure at the doses tested. One patient of 47 achieved a partial response and there was no correlation between tumor P-cadherin expression and clinical efficacy. Because of limited antitumor activity at the MTD level, Novartis has terminated clinical development of PCA062 (NCT02375958).

Co-Targeting of MDM2 and CDK4/6 with Siremadlin and Ribociclib for the Treatment of Patients with Well-Differentiated or Dedifferentiated Liposarcoma: Results from a Proof-of-Concept, Phase Ib Study.

PURPOSE: Well-differentiated (WDLPS) and dedifferentiated (DDLPS) liposarcoma are characterized by co-amplification of the murine double minute-2 (MDM2) and cyclin-dependent kinase-4 (CDK4) oncogenes. Siremadlin, a p53-MDM2 inhibitor, was combined with ribociclib, a CDK4/6 inhibitor, in patients with locally advanced/metastatic WDLPS or DDLPS who had radiologically progressed on, or despite, prior systemic therapy. PATIENTS AND METHODS: In this proof-of-concept, phase Ib, dose-escalation study, patients received siremadlin and ribociclib across different regimens until unacceptable toxicity, disease progression, and/or treatment discontinuation: Regimen A [4-week cycle: siremadlin once daily (QD) and ribociclib QD (2 weeks on, 2 weeks off)], Regimen B [3-week cycle: siremadlin once every 3 weeks; ribociclib QD (2 weeks on, 1 week off)], and Regimen C [4-week cycle: siremadlin once every 4 weeks; ribociclib QD (2 weeks on, 2 weeks off)]. The primary objective was to determine the maximum tolerated dose (MTD) and/or recommended dose for expansion (RDE) of siremadlin plus ribociclib in one or more regimens. RESULTS: As of October 16, 2019 (last patient last visit), 74 patients had enrolled. Median duration of exposure was 13 (range, 1-174) weeks. Dose-limiting toxicities occurred in 10 patients, most of which were Grade 3/4 hematologic events. The RDE was siremadlin 120 mg every 3 weeks plus ribociclib 200 mg QD (Regimen B). Three patients achieved a partial response, and 38 achieved stable disease. One patient (Regimen C) died as a result of treatment-related hematotoxicity. CONCLUSIONS: Siremadlin plus ribociclib demonstrated manageable toxicity and early signs of antitumor activity in patients with advanced WDLPS or DDLPS.

Results from a First-in-Human Phase I Study of Siremadlin (HDM201) in Patients with Advanced Wild-Type TP53 Solid Tumors and Acute Leukemia.

PURPOSE: This phase I, dose-escalation study investigated the recommended dose for expansion (RDE) of siremadlin, a p53-MDM2 inhibitor, in patients with wild-type TP53 advanced solid or hematologic cancers. PATIENTS AND METHODS: Initial dosing regimens were: 1A (day 1; 21-day cycle; dose 12.5-350 mg) and 2A (days 1-14; 28-day cycle; dose 1-20 mg). Alternative regimens included 1B (days 1 and 8; 28-day cycle) and 2C (days 1-7; 28-day cycle). The primary endpoint was incidence of dose-limiting toxicities (DLT) during cycle 1. RESULTS: Overall, 115 patients with solid tumors and 93 with hematologic malignancies received treatment. DLTs occurred in 8/92 patients with solid tumors and 10/53 patients with hematologic malignancies. In solid tumors, an RDE of 120 mg was defined in 1B. In hematologic tumors, RDEs were defined in 1A: 250 mg, 1B: 120 mg, and 2C: 45 mg. More patients with hematologic malignancies compared with solid tumors experienced grade 3/4 treatment-related adverse events (71% vs. 45%), most commonly resulting from myelosuppression. These were more frequent and severe in patients with hematologic malignancies; 22 patients exhibited tumor lysis syndrome. Overall response rates at the RDEs were 10.3% [95% confidence interval (CI), 2.2-27.4] in solid tumors and 4.2% (95% CI, 0.1-21.1), 20% (95% CI, 4.3-48.1), and 22.2% (95% CI, 8.6-42.3) in acute myeloid leukemia (AML) in 1B, 1A, and 2C, respectively. CONCLUSIONS: A common safety profile was identified and preliminary activity was noted, particularly in AML. Comprehensive investigation of dosing regimens yielded recommended doses/regimens for future combination studies.

Pharmacokinetic-pharmacodynamic guided optimisation of dose and schedule of CGM097, an HDM2 inhibitor, in preclinical and clinical studies.

BACKGROUND: CGM097 inhibits the p53-HDM2 interaction leading to downstream p53 activation. Preclinical in vivo studies support clinical exploration while providing preliminary evidence for dosing regimens. This first-in-human phase I study aimed at assessing the safety, MTD, PK/PD and preliminary antitumor activity of CGM097 in advanced solid tumour patients (NCT01760525). METHODS: Fifty-one patients received oral treatment with CGM097 10-400 mg 3qw (n = 31) or 300-700 mg 3qw 2 weeks on/1 week off (n = 20). Choice of dose regimen was guided by PD biomarkers, and quantitative models describing the effect of CGM097 on circulating platelet and PD kinetics. RESULTS: No dose-limiting toxicities were reported in any regimens. The most common treatment-related grade 3/4 AEs were haematologic events. PK/PD models well described the time course of platelet and serum GDF-15 changes, providing a tool to predict response to CGM097 for dose-limiting thrombocytopenia and GDF-15 biomarker. The disease control rate was 39%, including one partial response and 19 patients in stable disease. Twenty patients had a cumulative treatment duration of >16 weeks, with eight patients on treatment for >32 weeks. The MTD was not determined. CONCLUSIONS: Despite delayed-onset thrombocytopenia frequently observed, the tolerability of CGM097 appears manageable. This study provided insights on dosing optimisation for next-generation HDM2 inhibitors. TRANSLATIONAL RELEVANCE: Haematologic toxicity with delayed thrombocytopenia is a well-known on-target effect of HDM2 inhibitors. Here we have developed a PK/PD guided approach to optimise the dose and schedule of CGM097, a novel HDM2 inhibitor, using exposure, platelets and GDF-15, a known p53 downstream target to predict patients at higher risk to develop thrombocytopenia. While CGM097 had shown limited activity, with disease control rate of 39% and only one patient in partial response, the preliminary data from the first-in-human escalation study together with the PK/PD modeling provide important insights on how to optimize dosing of next generation HDM2 inhibitors to mitigate hematologic toxicity.

Translational Modeling of Anticancer Efficacy to Predict Clinical Outcomes in a First-in-Human Phase 1 Study of MDM2 Inhibitor HDM201.

We report on a retrospective model-based assessment of the predictive value of translating antitumor drug activity from in vivo experiments to a phase I clinical study in cancer patients treated with the MDM2 inhibitor, HDM201. Tumor growth inhibition models were developed describing the longitudinal tumor size data in human-derived osteosarcoma xenograft rats and in 96 solid tumor patients under different HDM201 treatment schedules. The model structure describing both datasets captures the delayed drug effect on tumor growth via a series of signal transduction compartments, including a resistance component. The models assumed a drug-killing effect on both sensitive and resistant cells and parameterized to estimate two tumor static plasma drug concentrations for sensitive (TSCS) and resistant cells (TSCR). No change of TSCS and TSCR with schedule was observed, implying that antitumor activity for HDM201 is independent of treatment schedule. Preclinical and clinical model-derived TSCR were comparable (48 ng/mL vs. 74 ng/mL) and demonstrating TSCR as a translatable metric for antitumor activity in clinic. Schedule independency was further substantiated from modeling of clinical serum growth differentiation factor-15 (GDF-15) as a downstream marker of p53 pathway activation. Equivalent cumulative induction of GDF-15 was achieved across schedules when normalized to an equivalent total dose. These findings allow for evaluation of optimal dosing schedules by maximizing the total dose per treatment cycle while mitigating safety risk with periods of drug holiday. This approach helped guide a phase I dose escalation study in the selection of an optimal dose and schedule for HDM201.

Inhibition of MDM2 Promotes Antitumor Responses in p53 Wild-Type Cancer Cells through Their Interaction with the Immune and Stromal Microenvironment.

p53 is a transcription factor that plays a central role in guarding the genomic stability of cells through cell-cycle arrest or induction of apoptosis. However, the effects of p53 in antitumor immunity are poorly understood. To investigate the role of p53 in controlling tumor-immune cell cross-talk, we studied murine syngeneic models treated with HDM201, a potent and selective second-generation MDM2 inhibitor. In response to HDM201 treatment, the percentage of dendritic cells increased, including the CD103+ antigen cross-presenting subset. Furthermore, HDM201 increased the percentage of Tbet+Eomes+ CD8+ T cells and the CD8+/Treg ratio within the tumor. These immunophenotypic changes were eliminated with the knockout of p53 in tumor cells. Enhanced expression of CD80 on tumor cells was observed in vitro and in vivo, which coincided with T-cell-mediated tumor cell killing. Combining HDM201 with PD-1 or PD-L1 blockade increased the number of complete tumor regressions. Responding mice developed durable, antigen-specific memory T cells and rejected subsequent tumor implantation. Importantly, antitumor activity of HDM201 in combination with PD-1/PD-L1 blockade was abrogated in p53-mutated and knockout syngeneic tumor models, indicating the effect of HDM201 on the tumor is required for triggering antitumor immunity. Taken together, these results demonstrate that MDM2 inhibition triggers adaptive immunity, which is further enhanced by blockade of PD-1/PD-L1 pathway, thereby providing a rationale for combining MDM2 inhibitors and checkpoint blocking antibodies in patients with wild-type p53 tumors. SIGNIFICANCE: This study provides a mechanistic rationale for combining checkpoint blockade immunotherapy with MDM2 inhibitors in patients with wild-type p53 tumors.

TGFß-blockade uncovers stromal plasticity in tumors by revealing the existence of a subset of interferon-licensed fibroblasts.

Despite the increasing interest in targeting stromal elements of the tumor microenvironment, we still face tremendous challenges in developing adequate therapeutics to modify the tumor stromal landscape. A major obstacle to this is our poor understanding of the phenotypic and functional heterogeneity of stromal cells in tumors. Herein, we perform an unbiased interrogation of tumor mesenchymal cells, delineating the co-existence of distinct subsets of cancer-associated fibroblasts (CAFs) in the microenvironment of murine carcinomas, each endowed with unique phenotypic features and functions. Furthermore, our study shows that neutralization of TGFß in vivo leads to remodeling of CAF dynamics, greatly reducing the frequency and activity of the myofibroblast subset, while promoting the formation of a fibroblast population characterized by strong response to interferon and heightened immunomodulatory properties. These changes correlate with the development of productive anti-tumor immunity and greater efficacy of PD1 immunotherapy. Along with providing the scientific rationale for the evaluation of TGFß and PD1 co-blockade in the clinical setting, this study also supports the concept of plasticity of the stromal cell landscape in tumors, laying the foundation for future investigations aimed at defining pathways and molecules to program CAF composition for cancer therapy.

Preclinical evaluation of drug combinations identifies co-inhibition of Bcl-2/XL/W and MDM2 as a potential therapy in uveal melanoma.

INTRODUCTION: Uveal melanoma (UM) is a rare and malignant intraocular tumour with a dismal prognosis. Despite a good control of the primary tumour by radiation or surgery, up to 50% of patients subsequently develop metastasis for which no efficient treatment is yet available. METHODOLOGY: To identify therapeutic opportunities, we performed an in vitro screen of 30 combinations of different inhibitors of pathways that are dysregulated in UM. Effects of drug combinations on viability, cell cycle and apoptosis were assessed in eight UM cell lines. The best synergistic combinations were further evaluated in six UM patient-derived xenografts (PDXs). RESULTS: We demonstrated that the Bcl-2/XL/W inhibitor (ABT263) sensitised the UM cell lines to other inhibitors, mainly to mammalian target of rapamycin (mTOR), mitogen-activated protein kinase kinase (MEK) and murine double minute 2 (MDM2) inhibitors. mTOR (RAD001) and MEK1/2 (trametinib) inhibitors were efficient as single agents, but their combinations with ABT263 displayed no synergism in UM PDXs. In contrast, the combination of ABT263 with MDM2 inhibitor (HDM201) showed a trend for a synergistic effect. CONCLUSION: We showed that inhibition of Bcl-2/XL/W sensitised the UM cell lines to other treatments encouraging investigation of the underlying mechanisms. Furthermore, our findings highlighted Bcl-2/XL/W and MDM2 co-inhibition as a promising strategy in UM.