SUMMARY  

• The interference of TECVAYLI with immunofixation methods required to confirm complete response (CR) per International Myeloma Group (IMWG) criteria have not been currently assessed.¹
• Since teclistamab is a modified immunoglobulin G (IgG) lambda antibody, interference with immunofixation assays could not be excluded.²
• Based on interim results (data cut-off: 16 March 2022) from patients who received teclistamab at the recommended phase 2 dose in the pivotal trial, CR was adjudicated in a similar fraction of subjects with IgG kappa and IgG lambda M protein, although time to CR was slightly longer for subjects with IgG lambda MM.²
• Although the small sample size does not allow for definitive conclusions, these current data would suggest that the interference of teclistamab in the assessment of CR by immunofixation might be limited.²
• Additional data have been identified and are included below for your reference.

Additional data

Kadkhoda et al (2024)³ reported the case of a 70-year-old male with relapsed or refractory multiple myeloma (RRMM) observed to have abnormal migration on serum protein electrophoresis (SPEP) and immunofixation electrophoresis (IFE) while receiving TECVAYLI.

• Disease characteristics: The patient was diagnosed with IgM/lambda multiple myeloma (MM), with atypical presentation of symptomatic hyperviscosity secondary to a detectable M-spike (59.6 g/L). Genetic testing identified high-risk disease features, including CDKN2C and 1q21 locus gains. Despite a disease course complicated by an acquired von Willebrand disease, the patient tolerated therapy well until biochemical disease progression in May 2019. The patient received multiple lines of therapy over 5 years, including treatment with chemotherapy and with monoclonal antibodies. After March 2022, the patient did not receive daratumumab or other monoclonal antibodies.
• TECVAYLI treatment: In January 2023, the patient started TECVAYLI after experiencing progressive disease. Prior to TECVAYLI initiation, routine monitoring revealed IgM/lambda monoclonal gammopathy. The patient received a total of 6 doses of TECVAYLI between January 10 and February 7. IgM/lambda monoclonal gammopathy persisted in serum tested on January 10 and January 30. On February 28, 2023, serum tested showed a prominent IgG/kappa band on IFE alongside IgM/lambda, which was interpreted as biclonal gammopathy. Additionally, SPEP showed a significant rise in M-protein levels (68.3 g/L from a baseline level of 7.1 g/L). The patient passed away before additional follow-up could be completed.

Whitt et al (2024)⁴ assessed the interference of TECVAYLI on routine SPEP and IFE analyses through retrospective review of electronic medical records. In multiple patients with refractory MM treated with TECVAYLI, IFE revealed IgG lambda or lambda light chain monoclonal proteins, which were inconsistent with previous immunofixation results. In one patient with IgG/lambda MM, SPEP showed spiking TECVAYLI increased the M-spike by approximately 0.15 g/dL.

Literature Search

A literature search of MEDLINE^®, Embase^®, BIOSIS Previews^®, and Derwent Drug File databases (and/or other resources, including internal/external databases) was conducted on 17 January 2025.