BCMA (B-cell maturation antigen, TNFRSF17) expression on plasma cells in relapsed/refract...

Deterministic view of the source YAML entity. Clinical authority remains with the cited source IDs and reviewer sign-off state.

ID	`RF-MM-BCMA-EXPRESSION-POS`
Type	Red flag
Status	reviewed 2026-04-29 \| pending_clinical_signoff
Diseases	`DIS-MM`
Sources	`SRC-ESMO-MM-2023` `SRC-MAJESTEC-1-MOREAU-2022` `SRC-NCCN-MM-2025`

Red Flag Origin

Definition	BCMA (B-cell maturation antigen, TNFRSF17) expression on plasma cells in relapsed/refractory multiple myeloma — universally expressed on malignant plasma cells (>99% of MM); IHC / flow cytometric confirmation typically not required for clinical eligibility but expression-loss escape on prior BCMA-directed therapy is a known mechanism. Gates BCMA-targeting agents 4L+: teclistamab (BCMAxCD3 BiTE; MajesTEC-1 Moreau 2022 NEJM — ORR 63%, CR 39.4%, mPFS 11.3 mo, mDOR 21.6 mo), elranatamab (MagnetisMM-3), and BCMA-directed CAR-T (ide-cel KarMMa, cilta-cel CARTITUDE-1). Triple-class-exposed (TCE) refractory MM cohort. Expression-loss / antigen-escape after prior BCMA exposure is a tracked composite — re-biopsy advised before sequencing a second BCMA agent.
Clinical direction	intensify
Category	high-risk-biology

Trigger Logic

{
  "all_of": [
    {
      "any_of": [
        {
          "finding": "bcma_expression",
          "value": "positive"
        },
        {
          "finding": "bcma_status",
          "value": "expressed"
        },
        {
          "finding": "bcma_ihc",
          "value": "positive"
        },
        {
          "finding": "bcma_flow",
          "value": "positive"
        }
      ]
    },
    {
      "any_of": [
        {
          "comparator": ">=",
          "finding": "prior_lines_count",
          "threshold": 3
        },
        {
          "finding": "triple_class_exposed",
          "value": true
        },
        {
          "finding": "triple_class_refractory",
          "value": true
        },
        {
          "finding": "penta_refractory",
          "value": true
        }
      ]
    }
  ],
  "type": "composite_score"
}

Notes

BCMA is expressed on >99% of MM plasma cells at diagnosis — RF gate is not "do you have BCMA" but rather "is patient TCE/penta-refractory AND BCMA-naive (or re-biopsied for re-expression)". Common AEs: cytokine release syndrome (CRS) ~70% any grade / <2% G3+, ICANS ~3%, infections G3+ ~45% (notable for hypogammaglobulinemia + opportunistic infection — IVIG replacement protocol expected). Antigen-escape mechanisms: BCMA loss-of-expression, BCMA mutation, γ-secretase upregulation. Pre-treatment IVIG threshold IgG <400 mg/dL. Sequencing question (BCMA-BiTE → BCMA-CAR-T vs reverse) is open research; CARTITUDE-4 + MajesTEC-1 cohort C inform. STUB — requires clinical co-lead signoff.

Used By

No reverse references found in the YAML corpus.