Background: Background: Teclistamab (JNJ-64007957) is a T cell redirecting bispecific antibody that targets both B-cell maturation antigen (BCMA) and CD3 receptors to induce T cell mediated cytotoxicity of BCMA-expressing myeloma cells. MajesTEC-1 is an open-label, multicohort, phase 1/2 study evaluating teclistamab in patients (pts) with relapsed/ refractory multiple myeloma (RRMM) previously treated with ≥3 prior lines of therapy (LOT). An overall response rate (ORR) of 62.0% in pts with no prior anti-BCMA treatment (tx) was previously reported in a pooled analysis from phase 1 and phase 2 cohort A at a median follow-up of 7.8 mo. Aims:Aims: We report efficacy and safety results of teclistamab from cohort C, which enrolled patients who had prior exposure to anti-BCMA treatment. Methods:Methods: Eligible pts (age ≥18 y) had multiple myeloma (MM) per IMWG criteria and were previously treated with ≥3 prior LOT, including a PI, IMiD, anti-CD38 antibody, and anti-BCMA treatment (chimeric antigen receptor T cell therapy [CAR-T] or Ab drug conjugate [ADC]). Pts were enrolled using a Simon's stage design to receive weekly subcutaneous teclistamab 1.5 mg/kg (step-up doses of 0.06 and 0.3 mg/kg). ORR per IMWG 2016 criteria was the primary endpoint. All AEs were graded per CTCAE v4.03; immune effector cell-associated neurotoxicity syndrome (ICANS) and cytokine release syndrome (CRS) were graded per ASTCT guidelines.