Preclinical activity of the BCMA/GPRC5D-dual-targeting trispecific antibody ramantamig (JNJ-5322) in multiple myeloma
BCMA- and GPRC5D-targeting bispecific antibodies (BsAbs) have shown unprecedented clinical efficacy in heavily pretreated MM patients. However, not all patients respond and most develop progressive disease. Dual-targeting T-cell immunotherapies may improve efficacy by addressing the issue of heterogeneous target expression and antigen escape.
BM samples from newly diagnosed (ND) or relapsed/refractory MM (RRMM) with exposure to IMiD and PI (double-class exposed), or RRMM with exposure to IMiD, PI, and daratumumab (triple-class exposed) were phenotyped and incubated with JNJ-5322 (0.032-5 nM) or mono-targeting BsAb controls (BCMAxCD3, GPRC5DxCD3). Luciferase-transduced MM cell lines were incubated with JNJ-5322 (0.008-25 nM) and T-cells from healthy donors (HD) or MM patients, including BsAb-exposed patients. MM cell lysis was assessed by flow cytometry and bioluminescence assay after 48 hours, respectively.
BCMA and GPRC5D expression on the MM cell surface in patient BM samples was highly heterogeneous (n=42). Some tumors had a predominantly BCMA- and GPRC5D- co-expressing population (mean 61%), while other tumors had populations only expressing BCMA (mean 15%) or GPRC5D (mean 12%), or neither (mean 12%).
JNJ-5322 was significantly more effective than mono-targeting BsAbs in 3 double positive MM cell lines with HD T-cells, and also efficiently eliminated 2 single-positive MM cell lines. T-cells from BsAb-exposed patients induced lower lysis of the MM cell line RPMI-8226 compared to BsAb-naïve patient T-cells. JNJ-5322 induced MM cell lysis in all 32 MM patient BM samples (median lysis with 0.4 nM: 59%), accompanied by T-cell activation, degranulation, cytokine and granzyme B release. BCMA- and GPRC5D-targeting BsAbs induced significantly lower MM cell lysis (median with 0.4 nM: 7% and 15%, respectively) in BM samples versus JNJ-5322, underscoring the benefit of dual-antigen targeting. JNJ-5322-mediated lysis of MM cells from ND, double-class exposed or triple-class exposed MM patients was comparable.
Tumor cell target expression was a critical determinant of response, shown by superior MM cell lysis in samples with higher than median baseline proportion of GPRC5D/BCMA double-positive MM cells, versus lower than median (25.6 fold shift in EC50). A high baseline frequency of PD-1 + or TIGIT + CD8 + T-cells impaired MM cell lysis, T-cell activation and degranulation. High-risk cytogenetic abnormalities [del(17p), t(4;14), and/or t(14;16)] did not influence JNJ-5322 efficacy.
Dual-antigen targeting with JNJ-5322 enhanced MM cell lysis versus combining the two mono-targeting BsAbs, in both cell lines and in 32 BM samples (median lysis at 0.4 nM: 59% versus 20%, respectively), possibly by increasing the overall avidity of the interaction.
Dual-antigen targeting with JNJ-5322 is more effective than mono-targeting BsAbs alone or in combination. Target expression and the frequency of PD-1 + or TIGIT + CD8 + T cells contribute to variability in ex vivo response to JNJ-5322.