Multiple myeloma (MM) care is undergoing rapid evolution, driven by maturing data for T‑cell–redirecting therapies, the formalization of measurable residual disease (MRD) as a regulatory endpoint, and practical advances that enable outpatient delivery and improved safety. This review summarizes the most practice-relevant developments over the past 2–3 years, emphasizing data likely to change care in the next 24–36 months across the US, EU, and China.
Cellular Therapies: BCMA- and GPRC5D-Directed CAR‑T
Randomized phase 3 trials have confirmed that B‑cell maturation antigen (BCMA)–directed CAR‑T therapies outperform standard regimens in relapsed/refractory MM (RRMM), supporting movement to earlier lines. In lenalidomide‑refractory patients after 1–3 prior lines, ciltacabtagene autoleucel (cilta‑cel) markedly prolonged PFS versus pomalidomide‑ or bortezomib‑based triplets (HR ≈ 0.26), increased MRD negativity (89% vs 38%), and showed favorable safety (CRS ≥G3 ≈1%; ICANS all ≤G2 ≈5%) 20. In triple‑class–exposed RRMM, idecabtagene vicleucel (ide‑cel) improved PFS (13.8 vs 4.4 months; HR 0.49) and CR rate, with manageable CRS/ICANS 20. Long‑term cilta‑cel follow‑up in late‑line disease shows sustained durability (median PFS 34.9 months; median OS 60.6 months; MRD negative in 92% evaluable), underscoring the depth achievable with single‑infusion therapy 20.
Multiple next‑generation autologous CAR‑T programs (US/China) report high response and MRD‑negativity rates with largely low‑grade CRS and low neurotoxicity, potentially broadening access:
- Anito‑cel (ddBCMA): ORR 97%, ≥CR 68%, MRD negativity 93%, 12‑month PFS 78.8% 20.
- Equecabtagene autoleucel (China): ORR 96.1%, sCR/CR 77.7%, MRD negativity 94.2%, 12‑month PFS 85.5% 20.
- Zevor‑cel: ORR 92.2%, sCR/CR 71.6%, durable responses at 18 months ~60% 20.
GPRC5D‑directed CAR‑T has emerged as a potent option after BCMA therapy. A phase II single‑arm study of anti‑GPRC5D CAR‑T (n=33) showed 91% ORR with 79% bone marrow MRD negativity, including 100% responses in patients previously treated with anti‑BCMA CAR‑T, and only grade 1–2 CRS in 76% (no grade ≥3 CRS) 2. A comparative meta‑analysis suggests higher ORR and CR, and lower relapse with GPRC5D CAR‑T versus BCMA CAR‑T (ORR 89.8% vs 76.3%; CR 50.5% vs 34.3%; relapse 26.0% vs 57.3%), with low rates of grade 3–5 CRS and ICANS in both groups 7. Early GPRC5D CAR‑T data (OriCAR‑017) show 100% ORR with 100% MRD negativity at day 28 and 3 months, and only low‑grade CRS 20.
Allogeneic (off‑the‑shelf) CAR‑T platforms (e.g., ALLO‑715) enable rapid treatment (~5 days to infusion) without graft‑versus‑host disease and with mostly low‑grade CRS, but durability and persistence require optimization 20. In‑vivo BCMA CAR‑T generation (without conventional ex vivo manufacturing, with conditioning approaches still under investigation) has achieved MRD negativity in early proof‑of‑concept patients with low‑grade CRS and no neurotoxicity; broader validation is pending and could markedly simplify logistics 1333.
Bispecific T‑Cell Engagers (BsAbs): BCMA and GPRC5D
BCMA × CD3 and GPRC5D × CD3 bispecific antibodies are delivering high response rates with subcutaneous outpatient dosing, although infection management is critical.
- Teclistamab (BCMA × CD3): ORR ~63%, ≥CR ~46%, median DOR ~24 months; CRS ~72% (mostly grade 1–2). Prophylactic tocilizumab during step‑up dosing reduces CRS to ~25% without apparent efficacy loss 113. In the phase 3 MajesTEC‑3 study (teclistamab + daratumumab vs DPd/DVd, 1–3 prior lines), 36‑month PFS was 83.4% vs 29.7% (HR 0.17), OS favored the bispecific combination, and MRD‑negative CR (10⁻⁵) reached 57.6% vs 17.1%. Infection‑related deaths were mitigated after adoption of systematic IVIG replacement (0.4 g/kg monthly for hypogammaglobulinemia) 34.
- Elranatamab (BCMA × CD3): ORR 61%, ≥CR 37%, median PFS 17.2 months; less‑frequent maintenance dosing (Q2W/Q4W) maintains efficacy 2043.
- Linvoseltamab (BCMA × CD3): ORR ~71% at 200 mg; ≥CR ~50%; median DOR ~29 months; lower tumor burden (sBCMA <400 ng/mL) correlates with higher ORR 20.
- Talquetamab (GPRC5D × CD3): ORR 67–74% with durability on Q2W schedules. Class‑specific oral/skin adverse effects (dysgeusia, rash, nail disorders) are frequent but typically low‑grade; severe infections appear comparatively lower than with BCMA BsAbs. Activity persists after prior T‑cell–redirecting therapy 1720.
Dual‑bispecific combinations (talquetamab + teclistamab) show deep activity in extramedullary disease (ORR 79%, ≥CR 54%, median PFS 15 months), with many patients maintaining/deepening responses after de‑escalation to monthly dosing. Infection risk is substantial (any‑grade 80%, grade 3/4 33%); IVIG and antimicrobial prophylaxis are essential 3420.
Outpatient feasibility is increasingly established. European experts reached strong consensus that outpatient step‑up dosing is feasible with appropriate selection and prophylaxis; implementation is underway across multiple countries 3. US community cohorts demonstrate safe step‑up completion and continued outpatient dosing with low rates of ICANS and no treatment discontinuations due to CRS 3536. Prophylactic tocilizumab reduces CRS during step‑up 3, and standardized infection prophylaxis (including IVIG) reduces serious infections 3444.
A key design lesson: reduced CD3 affinity alone (e.g., REGN5459) did not eliminate CRS, underscoring the role of tumor burden and T‑cell activation as primary CRS drivers 5.
MRD‑Driven Decision‑Making: From Prognostic to Actionable
MRD has moved from a prognostic biomarker to a regulatory endpoint and is increasingly guiding clinical decisions:
- Regulatory recognition: The FDA defines MRD negativity (flow cytometry or sequencing in CR/sCR) as a valid primary endpoint for accelerated approval, formalizing its use for response assessment and therapy modification 42.
- Prognostic value: Post‑transplant patients achieving MRD negativity (10⁻⁶) have superior outcomes; sustained MRD negativity confers the best prognoses 2123. Across randomized trials, increases in MRD negativity track with PFS benefits, supporting MRD as a surrogate endpoint 52.
- MRD in T‑cell redirecting therapy: Post‑CAR‑T MRD negativity at day 90 by ctDNA correlates strongly with prolonged time to progression (TTP) and aligns with bone marrow NGS MRD 1. In BsAb regimens, MRD negativity rates are high in earlier‑line combinations (e.g., MajesTEC‑3) and maintenance/de‑escalation cohorts 3420.
- MRD‑adapted strategies: Randomized and prospective trials in newly diagnosed MM (NDMM) show MRD‑driven intensification can deepen responses and improve PFS (e.g., AURIGA: daratumumab+lenalidomide converted 50.5% to MRD negative by 12 months vs 18.8% with lenalidomide; HR 0.53 for PFS) 47. Quadruplet D‑VRd improved MRD negativity and PFS in transplant‑ineligible/deferred (CEPHEUS) and transplant‑eligible (PERSEUS) NDMM 4853. FORTE confirmed clinical equivalence of next‑generation flow (NGF) and NGS at matched sensitivity, enabling flexible MRD implementation 49. MRD‑guided de‑escalation (e.g., transplant omission or therapy cessation) is under investigation and gaining visibility, but definitive, widely generalizable stopping rules remain to be confirmed in randomized datasets not fully contained in the retrieved materials 3723.
Two important caveats for MRD interpretation in immunotherapy:
- Circulating CAR‑derived DNA can be detected and may confound NGS‑based MRD interpretation; assays and clinicians must distinguish CAR sequences from tumor clones 6.
- BCMA+ plasma cell re‑emergence in marrow predicts clinical relapse post‑BCMA CAR‑T and often precedes it, advocating for vigilant MRD surveillance to enable early intervention 18.
Diagnostics and Biomarkers: Liquid Biopsy, Mass Spectrometry, Imaging, and Genomics
- ctDNA by CAPP‑Seq: Correlates with conventional markers; day‑90 ctDNA MRD negativity after BCMA CAR‑T predicts prolonged TTP; detects resistance mechanisms (e.g., emergent BCMA copy loss in 17% of relapses; baseline BCMA loss associates with shorter TTP). CAR‑derived cfDNA mirrors CAR‑T expansion and inversely correlates with tumor burden, enabling dual tracking of expansion and response 1.
- Mass spectrometry MRD: Blood‑based clonotypic mass spectrometry after autologous transplant associates with PFS/OS and offers minimally invasive serial monitoring 24. MALDI‑TOF–based assays during maintenance show 70% agreement with bone marrow MRD, and “double negative” (blood MS and BM MRD) confers superior PFS; sustained MS negativity is prognostic 51.
- Imaging: PET‑CT may show early “flare” after BsAb therapy despite biochemical response, cautioning against premature progression calls; integration with MRD and clinical context is advised 25.
- Risk genomics: A 2025 Nature Genetics score refines baseline risk stratification 28. Clonal hematopoiesis may influence BCMA CAR‑T outcomes and warrants consideration in pre‑treatment risk assessments 26. GPRC5D’s lack of antigen shedding may reduce sink effects and support better persistence for GPRC5D‑targeted therapies 4. Lower soluble BCMA (sBCMA) levels may predict higher response with linvoseltamab 20.
Changes in Clinical Practice: Frontline, Relapsed/Refractory, and Post‑Transplant
- Frontline: Anti‑CD38‑based quadruplets (D‑VRd; Isa‑RVd) are now supported by MRD and PFS gains across NDMM populations 485350. MRD‑adapted strategies (e.g., daratumumab‑based maintenance intensification for MRD‑positive post‑transplant patients) are demonstrating PFS advantages 47. BsAbs in frontline/maintenance are promising but remain investigational pending phase 3 confirmation and infection‑mitigation strategies 20.
- Relapsed/Refractory: Randomized superiority of BCMA CAR‑T over standard regimens supports earlier use in lenalidomide‑refractory disease 20. In parallel, BsAbs (teclistamab, elranatamab, talquetamab, linvoseltamab) are increasingly available with outpatient step‑up dosing and structured infection prophylaxis, enabling broader community adoption 11433536.
- Sequencing: The European Myeloma Network (EMN) recommends CAR‑T‑first sequencing when feasible, noting reduced efficacy of CAR‑T after BsAbs and strong post‑CAR efficacy of GPRC5D‑directed agents 1012. Other guidance and practice updates emphasize BsAb feasibility, outpatient delivery, and standardized infection prophylaxis/IVIG—leading some centers to prioritize BsAbs as the first T‑cell–redirecting therapy after conventional regimens, with CAR‑T reserved for BsAb‑refractory or rapidly progressive disease 434546. These differing positions reflect real‑world capacity constraints and local infrastructure rather than conflicting efficacy data.
- Supportive care: IVIG replacement and antimicrobial prophylaxis have become standard elements of BsAb and CAR‑T programs, with real‑world evidence showing dramatic reductions in severe infections and infection‑related mortality after protocolized IVIG adoption 3444. Prophylactic tocilizumab during step‑up dosing reduces CRS for BsAbs 3.
Emerging Technologies and Next‑Wave Innovations
- Dual‑target CAR‑T (e.g., BCMA/CD19): High ORR (up to 92%) with encouraging durability and low grade ≥3 CRS in early studies; aims to reduce antigen escape 81920.
- FcRH5‑targeted approaches: Preclinical FcRH5 CAR‑T and FcRH5/BCMA bispecific CAR‑T demonstrate robust activity and may address BCMA‑negative clones 15.
- Trispecific antibodies: Early clinical development of dual‑antigen/co‑stimulatory engagement to prevent T‑cell exhaustion; promising activity in small cohorts but infection risk management will be key 1737.
- In‑vivo CAR‑T manufacturing: Early human data suggest feasibility without leukapheresis/lymphodepletion and low toxicity; could democratize access if durable efficacy is confirmed 1333.
- Allogeneic CAR‑T: Off‑the‑shelf options (e.g., ALLO‑715) shorten time‑to‑treatment substantially but require improvements in persistence and infection management before broad adoption 20.
Comparative Snapshot: Key Efficacy, Durability, and Safety
- BCMA CAR‑T (randomized): cilta‑cel vs PVd/DPd—PFS HR 0.26, ≥CR 73% vs 22%, MRD negativity 89% vs 38%, CRS 76% (≥G3 1%), ICANS 5% (all ≤G2) 20.
- BCMA CAR‑T (randomized): ide‑cel vs standard—PFS 13.8 vs 4.4 months (HR 0.49), CR 44% vs 5%; manageable CRS/ICANS 20.
- GPRC5D CAR‑T: ORR 91% with 79% MRD negativity; low‑grade CRS; strong post‑BCMA activity 2; meta‑analysis favors GPRC5D over BCMA CAR‑T for response and relapse rates 7.
- BCMA BsAbs: teclistamab ORR 63%, ≥CR 46%, mDOR ~24 months; elranatamab ORR 61%, ≥CR 37%, mPFS 17.2 months; linvoseltamab ORR ~71%, ≥CR ~50%, mDOR ~29 months 112043.
- GPRC5D BsAb: talquetamab ORR 67–74%, durability with Q2W dosing; class‑specific on‑target off‑tumor AEs manageable 1720.
Near‑Term Practice Impact: Ranking and Rationale
- Earlier‑line BCMA CAR‑T in RRMM
- Why: Randomized superiority over standard regimens with deep MRD and favorable safety profile 20.
- Barrier: Center capacity, manufacturing slots, and payer logistics.
- Broad outpatient BsAb implementation with structured prophylaxis
- Why: High efficacy with subcutaneous dosing; real‑world feasibility; prophylactic tocilizumab lowers CRS; IVIG reduces infection‑related mortality 334353644.
- Barrier: Sustained infection risk and hypogammaglobulinemia necessitating rigorous supportive care.
- MRD‑integrated response assessment and therapy tailoring
- Why: FDA recognition of MRD as an endpoint; strong prognostic value; MRD‑driven intensification (e.g., D‑R maintenance) improves PFS 424752.
- Barrier: Generalizable stopping rules for de‑escalation remain under study; assay/interpretation complexities (e.g., CAR‑derived sequences) must be navigated 6.
- ctDNA/mass spectrometry for serial monitoring
- Why: ctDNA anticipates relapse and detects resistance (BCMA loss); MS offers minimally invasive MRD with prognostic power and complements bone marrow MRD 12451.
- Barrier: Assay standardization, access, and integration into reimbursement pathways.
- Post‑BCMA GPRC5D‑directed therapy
- Why: Robust efficacy after BCMA exposure for both CAR‑T and BsAbs; non‑shedding antigen may support persistence 27174.
- Barrier: Class‑specific toxicities (oral/dermatologic) and sequencing optimization.
- Dual‑target and in‑vivo CAR‑T platforms
- Why: Potential to prevent antigen escape and democratize access 81333.
- Barrier: Early‑phase maturity; durability and safety confirmation required.
Practical Implementation Notes
- Outpatient eligibility for BsAbs: functional status (ECOG <3), low tumor burden, controlled comorbidities, caregiver support, proximity to care; remote monitoring/home nursing augment safety 3.
- Infection prophylaxis: baseline viral screening; antivirals; antibacterial/antifungal prophylaxis during neutropenia; Pneumocystis prophylaxis; IVIG replacement for hypogammaglobulinemia, with protocols such as 0.4 g/kg monthly when IgG <4 g/L or with infections 44. Protocolized IVIG reduced infection‑related deaths in MajesTEC‑3 34.
- CRS/ICANS management: early tocilizumab for grade ≥2 CRS; corticosteroids for refractory CRS or ICANS; standardized pathways embedded into NCCN/EHA‑EMN practice updates facilitate broader adoption 4445.
Conclusion
The next 2–3 years will see earlier use of BCMA CAR‑T in RRMM, widespread outpatient adoption of BsAbs enabled by prophylactic tocilizumab and IVIG, and integration of MRD into routine decision‑making. Liquid biopsy (ctDNA) and mass spectrometry are poised to complement bone marrow MRD for serial surveillance and early relapse detection. GPRC5D‑directed therapies are solidifying as the preferred route after BCMA‑directed therapy. Dual‑target and in‑vivo CAR‑T platforms represent promising innovations with potential to broaden access and enhance durability. Regional adoption will hinge on capacity and infrastructure—particularly for CAR‑T—while supportive care standardization will be central to safe, scalable deployment of T‑cell–redirecting therapies across care settings 203344244.