A matching-adjusted indirect comparison of the efficacy of elranatamab versus physician's choice of treatment in patients with triple-class exposed/refractory multiple myeloma

INTRODUCTION

For patients with triple-class exposed/refractory multiple myeloma (TCE/R MM), prognosis is poor and effective treatment options are limited. Elranatamab is a novel B-cell maturation antigen (BCMA)- and CD3-directed bispecific antibody which was approved by the US Food and Drug Administration in August 2023 and demonstrated safety and efficacy in patients with TCE/R MM in the phase 2, single-arm MagnetisMM-3 trial (NCT04649359). To compare the effectiveness of elranatamab vs physician's choice of treatment (PCT) in the absence of head-to-head comparative data, a matching-adjusted indirect comparison (MAIC) was conducted.

METHODS

Individual patient data from MagnetisMM-3 (Cohort A [BCMA-naïve] N = 123, 14.7 months of follow-up) were reweighted to match published summary data from two real-world studies of PCT in patients with TCE/R MM (LocoMMotion and MAMMOTH) using a propensity score-type logistic regression. Unanchored MAIC analyses were conducted according to National Institute for Health and Care Excellence (NICE) Decision Support Unit (DSU) 18 guidance.

RESULTS

Compared with PCT in LocoMMotion, elranatamab was associated with a significantly higher objective response rate (ORR rate difference: 37.52; 95% CI 26.20-48.83; odds ratio: 4.85; 95% CI 2.85-8.23) and complete or stringent complete response rate (≥CR rate difference: 42.29; 95% CI 31.84-52.74; odds ratio: 184.01; 95% CI 24.66-1372.86), longer progression-free survival (PFS HR 0.32; 95% CI 0.20-0.49), and overall survival (OS HR 0.62; 95% CI 0.40-0.94). Compared with PCT in MAMMOTH, elranatamab was associated with significantly higher ORR (rate difference: 28.14; 95% CI 16.77-39.52; odds ratio: 3.24; 95% CI 1.98-5.32) and ≥ CR (rate difference: 26.22; 95% CI 16.40-36.05; odds ratio: 5.48; 95% CI 2.88-10.44), as well as longer PFS (HR 0.25; 95% CI 0.17-0.37) and OS (HR 0.49; 95% CI 0.33-0.71). Sensitivity analysis results were consistent with the base case.

CONCLUSION

In the MAIC, elranatamab was consistently associated with improved rates and depth of response and significantly longer PFS and OS versus PCT in LocoMMotion and MAMMOTH.

Image-Guided Surgery: Breast Cancer Detection Using Monoclonal Antibodies Conjugated to a Near-Infrared Fluorescent Dye in a Syngeneic Rat Model

Background: Incomplete tumor resections occur frequently in patients undergoing breast-conserving surgery. As the surgeon can only rely on palpation and visual inspection, real-time visualization of cancer cells during surgery is needed to increase the number of complete tumor resections. Near-infrared fluorescence (NIRF) imaging using an intra-operative camera system is a novel technique to assess the extent of disease during surgery. Advantages of NIRF light (700-900 nm) include high tissue penetration up to several centimeters deep and low autofluorescence providing sufficient signal-to-noise ratio. Currently, several NIRF dyes are available for chemical conjugation to molecules that can target tumors, e.g. antibodies. This study aimed to investigate whether monoclonal antibodies conjugated to a NIRF dye could detect primary breast carcinomas in a syngeneic rat model.Methods: The hormone-dependent syngeneic breast cancer rat model EMR86 and its derived cell line MCR86 were used. Tumors were induced by orthotopic implantation of fresh EMR86 tumor fragments of 1 mm3 into the flanks at four sites in female WAG/Rij rats (Harlan, the Netherlands). The mouse monoclonal antibody MG1 was used for tumor cell detection. MG1 (IgG2a) recognizes a membrane epitope of rat cancer cells of epithelial origin and is developed by our research group. MG1 was conjugated to the NIRF dye CW-800 (LI-COR, USA) and dye/protein ratio was determined using absorbance measurements (UltroSpec, Amersham, UK). Fluorescence imaging of cells, animals and organs was performed using IVIS Spectrum (Caliper, USA) and Odyssey (LI-COR, USA) equipment.Results: Conjugated antibodies MG1-CW800 bound specifically to cultured MCR86 cells. The signal intensity was linearly correlated with the number of cells and concentration of MG1-CW800 (R2=0.99, p<0.00001). Addition of unconjugated MG1 lowered the fluorescent signal in a competitive binding assay, showing that labeling did not influence binding properties. Intravenous injection of unconjugated MG1 (200 μg/rat) in 3 Wag/Rij rats and subsequent immunohistochemical analysis of tissue sections revealed a specific and exclusive binding of MG1 to the EMR86 tumors and no difference in staining intensity between 24 and 48hrs after injection. Intravenous injection of conjugated MG1-CW800 (200 μg/rat) demonstrated a clear fluorescent demarcation of EMR86 tumors and the surrounding tissue after spectral unmixing (paired t-test 8.17, p<0.00001). Mean fluorescence did not differ between 24 and 48hrs after injection (t=1.85, p=0.11). However, a two-fold increase of the dye/protein ratio led to a two-fold increase of the in vivo fluorescence (t=-6.40, p=0.0001).Conclusion: Intravenous injection of monoclonal antibodies MG1 conjugated to the NIRF dye CW800 enabled detection of primary breast carcinomas in the syngeneic hormone-dependent EMR86 rat model. This study demonstrates proof-of-concept for future labeling of clinically relevant antibodies (e.g. HER2/neu, EGF, VEGF). Translation of this technique to breast cancer patients can lead to intra-operative identification of optimal resection margins in order to increase the comple tumor resection rate.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5006.