ABSTRACT
PURPOSE: Immunomodulatory drugs (IMiDs), such as lenalidomide and pomalidomide, are a cornerstone of multiple myeloma (MM) therapies, yet the disease inevitably becomes refractory. IMiDs exert cytotoxicity by inducing cereblon-dependent proteasomal degradation of IKZF1 and IKZF3, resulting in downregulation of the oncogenic transcription factors IRF4 and MYC. To date, clinical IMiD resistance independent of cereblon or IKZF1/3 has not been well explored. Here, we investigated the roles of IRF4 and MYC in this context. EXPERIMENTAL DESIGN: Using bone marrow aspirates from patients with IMiD-naïve or refractory MM, we examined IKZF1/3 protein levels and IRF4/MYC gene expression following ex vivo pomalidomide treatment via flow cytometry and qPCR. We also assessed exvivo sensitivity to the MYC inhibitor MYCi975 using flow cytometry. RESULTS: We discovered that although pomalidomide frequently led to IKZF1/3 degradation in MM cells, it did not affect MYC gene expression in most IMiD-refractory samples. We subsequently demonstrated that MYCi975 exerted strong anti-MM effects in both IMiD-naïve and -refractory samples. Unexpectedly, we identified a cluster of differentiation 8+ (CD8+ T) cells from patients with MM as crucial effectors of MYCi975-induced cytotoxicity in primary MM samples, and we discovered that MYCi975 enhanced the cytotoxic functions of memory CD8+ T cells. We lastly observed synergy between MYCi975 and pomalidomide in IMiD-refractory samples, suggesting that restoring MYC downregulation can re-sensitize refractory MM to IMiDs. CONCLUSIONS: Our study supports the concept that MYC represents an Achilles' heel in MM across disease states and that MYCi975 may be a promising therapeutic for patients with MM, particularly in combination with IMiDs.
Subject(s)
CD8-Positive T-Lymphocytes , Drug Resistance, Neoplasm , Ikaros Transcription Factor , Immunomodulating Agents , Interferon Regulatory Factors , Multiple Myeloma , Proto-Oncogene Proteins c-myc , Thalidomide , Humans , Multiple Myeloma/drug therapy , Multiple Myeloma/pathology , Multiple Myeloma/immunology , CD8-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/drug effects , CD8-Positive T-Lymphocytes/metabolism , Proto-Oncogene Proteins c-myc/genetics , Proto-Oncogene Proteins c-myc/metabolism , Ikaros Transcription Factor/metabolism , Ikaros Transcription Factor/genetics , Thalidomide/analogs & derivatives , Thalidomide/pharmacology , Immunomodulating Agents/pharmacology , Interferon Regulatory Factors/metabolism , Interferon Regulatory Factors/genetics , Cell Line, Tumor , Lenalidomide/pharmacology , Lenalidomide/therapeutic use , Gene Expression Regulation, Neoplastic/drug effects , Female , MaleABSTRACT
T cell-engaging antibodies (TCEs) are showing promising efficacy in relapsed/refractory multiple myeloma, even in patients that relapsed after B-cell maturation antigen (BCMA)-targeted therapy. Patients with multiple myeloma may have compromised T-cell health unaccounted for by preclinical models. Here, we use Myeloma Drug Sensitivity Testing (My-DST) for ex vivo measurement of anti-multiple myeloma cytotoxicity for the trispecific CD38/CD28xCD3 TCE SAR442257 through activation of the patients' own endogenous T cells to inform clinical development of the compound in multiple myeloma. My-DST incubates primary mononuclear cells in humanized media for 48 hours followed by flow cytometry for multiple myeloma cell viability with or without drug treatment. SAR442257 was tested on 34 samples from patients with multiple myeloma across disease settings. Potential biomarkers, T-cell dependence, and degranulation were assessed. SAR442257 was effective at low dose in My-DST cultures. High ex vivo response rates were observed in primary aspirates taken from patients with multiple myeloma at diagnosis, with modestly reduced response in multiple myeloma recently treated with anti-CD38 mAbs. SAR442257 was highly effective in patients relapsing after BCMA therapy. The CD38/CD28xCD3 trispecific format was substantially more effective than a conventional bispecific CD38/CD3 antibody format and CD38 mAbs. Anti-multiple myeloma cell cytotoxicity was dependent on the presence of endogenous T cells. Surface CD38 expression was the strongest biomarker of TCE response. My-DST is capable of measuring T cell-dependent killing using the multiple myeloma patient's own bone marrow-derived T cells. SAR442257 shows promise for multiple myeloma and may be best suited for patients declared resistant to both CD38 mAbs and BCMA-targeted therapy. SIGNIFICANCE: This study introduces the use of My-DST to measure and characterize sensitivity to anti-CD38 T-cell engager SAR442257 in primary samples using matched endogenous T cells. Preclinical testing in samples from patients with diverse treatment history supports further testing in post-chimeric antigen receptor T-cell multiple myeloma.
Subject(s)
Antibodies, Monoclonal , Antineoplastic Agents , Multiple Myeloma , Humans , Multiple Myeloma/drug therapy , T-Lymphocytes , B-Cell Maturation Antigen/therapeutic use , ADP-ribosyl Cyclase 1 , Neoplasm Recurrence, Local/drug therapy , Antineoplastic Agents/therapeutic useABSTRACT
Monoclonal antibodies targeting CD38 are important for treatment of both newly diagnosed and relapsed multiple myeloma (MM). Daratumumab and isatuximab are anti-CD38 antibodies with the US Food and Drugs Administration approval in multiple different combinations. Despite good initial efficacy, patients inevitably develop drug resistance. Whether patients can be effectively re-treated with these antibodies in subsequent lines of therapy is unclear. Thus far, studies have mostly been limited to clinical retrospectives with short washout periods. To answer whether patients regain sensitivity after longer washouts, we used ex vivo sensitivity testing to isolate the anti-CD38 antibody-specific cytotoxicity in samples obtained from patients who had been exposed to and then off daratumumab for up to 53 months. MM cells from patients who had been off daratumumab for >1 year showed greater sensitivity than those with <1 year, although they still were less sensitive than those who were daratumumab naïve. CD38 expression on MM cells gradually recovered, although, again, not to the level of anti-CD38 antibody-naïve patients. Interestingly, low MM CD38 explained only 45% of cases identified to have daratumumab resistance. With clinical follow-up, we found ex vivo sensitivity predicted subsequent clinical response but CD38 overexpression did not. Patients clinically re-treated with anti-CD38 antibodies had <6 months of clinical benefit, but 1 patient who was daratumumab exposed but not refractory achieved complete response lasting 13 months. We conclude that transient efficacy can be achieved by waiting 1 year before CD38 antibody rechallenge, but this approach may be best used as a bridge to, or after, chimeric antigen receptor T-cell therapy.