Post-CAR-T Relapse in China: Active Bispecific and Trispecific Clinical Trials
Post-Cellular Rescue · Target Switching, GPRC5D, and Next-Generation Multispecifics
Medical Disclaimer: The following content is compiled based on the latest authoritative guidelines at home and abroad. It is for reference only for patients and their families and cannot replace the professional medical advice of the attending physician. Please be sure to follow the doctor's advice for the treatment plan.
Core Conclusion
While BCMA CAR-T therapies yield unprecedented response rates, post-infusion disease progression remains a recognized clinical reality. A post-CAR-T relapse does not mean treatment failure is permanent: switching to alternative tumor targets like GPRC5D via bispecific or trispecific antibodies represents China's leading frontline rescue pathway.
1. Mechanisms of Post-CAR-T Relapse
To design an effective rescue strategy, medical teams assess why the initial cell therapy failed:
- Antigen Downregulation and Loss: Under selective cytotoxic pressure from infused CAR-T cells, sub-clones with low or negative BCMA surface density emerge, rendering BCMA-targeted constructs blind.
- Effector T-Cell Exhaustion: Infused autologous CAR-T cells may undergo terminal exhaustion or rapid in vivo clearance due to severe chronic antigenic stimulation.
- Target Switching as the Standard Rescue: The consensus approach in Chinese clinical practice is switching target antigens, prioritizing non-BCMA mechanisms to re-engage cytotoxic T cells against fresh cell-surface markers.
2. The Dominance of GPRC5D and Multispecifics in China
The pipeline of active clinical trials in China for post-CAR-T relapses is exceptionally robust:
- GPRC5D Bispecific Antibodies: Off-the-shelf T-cell engagers targeting GPRC5D achieve overall response rates of 60%–70% even in patients with prior BCMA cellular therapy failure.
- Dual-Target and Trispecific Antibodies: Advanced constructs such as BCMA × GPRC5D × CD3 trispecific antibodies offer built-in insurance against single-antigen escape.
- Novel Allogeneic / Second CAR-T Formats: Investigational Phase 1 studies in leading academic centers explore dual-target CAR-T (BCMA/CD19 or BCMA/GPRC5D) for durable immunological resetting.
3. Practical Sequencing Checklist for Families
When preparing for post-CAR-T trial matching at a Chinese medical center:
- Obtain a Repeat Bone Marrow Biopsy: Essential to assess current BCMA and GPRC5D receptor density by immunohistochemistry or flow cytometry.
- Evaluate Treatment Kinetics: If disease progresses aggressively, prioritize off-the-shelf bispecific trials over cellular therapies requiring weeks of manufacturing.
- Monitor Supportive Care: Proactively initiate dermatological care and nutritional counseling if entering a GPRC5D-directed protocol.
This clinical trial analysis is published by China Myeloma Digital Network (CMDN) based on Chinese registrational data.
FAQs
- Does disease progression after BCMA CAR-T mean all therapeutic options are exhausted?
- No. Relapse after BCMA CAR-T represents one of the highest areas of clinical trial investment in China. By switching to alternative targets (such as GPRC5D or FcRH5) or utilizing multispecific T-cell redirection (bispecific and trispecific antibodies), high rates of deep second remissions are regularly achieved.
- Why do myeloma patients relapse after CAR-T, and what is 'antigen loss'?
- Relapse primarily occurs via three mechanisms: 1. Antigen escape or downregulation, where malignant plasma cells shed or downregulate surface BCMA expression; 2. Loss of CAR-T cellular persistence or exhaustion of engineered lymphocytes; 3. Emergence of an immunosuppressive bone marrow microenvironment.
- What is GPRC5D, and how does it differ from BCMA?
- GPRC5D (G-protein coupled receptor class C group 5 member D) is a distinct seven-transmembrane receptor highly expressed on malignant plasma cells, completely independent of BCMA. Even if myeloma cells lose BCMA expression entirely, GPRC5D-directed immunotherapies remain fully active.
- What is a trispecific antibody, such as a BCMA×GPRC5D×CD3 construct?
- Trispecific antibodies bind two distinct myeloma antigens (BCMA and GPRC5D) simultaneously while engaging CD3 on T cells. This dual-targeting mechanism ensures that even if tumor cells downregulate one antigen, the second binding domain continues to recruit T cells and sustain cytotoxic killing.
- What specific side effects are associated with GPRC5D-targeted therapies?
- Because GPRC5D is physiologically expressed in keratinized tissues (hair follicles, nail beds, and tongue papillae), targeted therapies can cause skin exfoliation, brittle nails, and dysgeusia (altered taste). These toxicities are generally mild to moderate and manageably reversed with moisturizers, nail care, and dietary adjustments.
Related reading
References used for this guide
Nationwide Clinical Trials for GPRC5D Bispecifics, Trispecifics & Target-Swapping Therapies
Frontline clinical trials targeting GPRC5D, FcRH5 and trispecific antibodies for post-BCMA relapse:
A Multicenter, Open-Label Phase II Study Evaluating QLS4131 for Injection in Combination Therapy for the Treatment of Malignant Plasma Cell Neoplasms
This study is a multicenter, open-label Phase II clinical trial evaluating the safety, tolerability, and preliminary efficacy of QLS4131 for injection in combination therapy in patients with malignant plasma cell neoplasms. The study plans to enroll participants aged 18 years and older with confirmed multiple myeloma, plasma cell leukemia, or primary light chain amyloidosis. The lead institution is Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, and the study is conducted across multiple hospitals nationwide.
A Phase I/II, Multicenter, Open-Label Study of IBI3003 in Participants with Relapsed or Refractory Multiple Myeloma
This project is a Phase I/II clinical trial sponsored by Innovent Biologics, primarily targeting patients with relapsed or refractory multiple myeloma who have received at least 2 prior lines of therapy (and must have previously received at least one proteasome inhibitor, one immunomodulatory drug, and one anti-CD38-based therapy). The treatment regimen utilizes an innovative biologic product (IBI3003 injection) administered according to the participant's body weight, with continuous treatment until disease progression, unacceptable toxicity, or a maximum routine treatment period of 24 months (patients deriving clinical benefit may continue treatment upon evaluation). This study is an international multicenter trial, currently with a total of 23 leading general and specialized hospitals participating in China, including core hematology diagnosis and treatment institutions such as the First Affiliated Hospital of Soochow University, the First Affiliated Hospital, Zhejiang University School of Medicine, Beijing Chaoyang Hospital, Capital Medical University, Tianjin Medical University General Hospital, and Xiangya Hospital Central South University.
An Open-Label, Multicenter Clinical Study Evaluating the Safety, Pharmacokinetics, and Efficacy of OriCAR-017 in Participants with Relapsed/Refractory Multiple Myeloma (MERCURY)
This project is a Phase Ib/II clinical trial sponsored by OrigiCell Therapeutics (Shanghai) Co., Ltd., primarily enrolling patients with relapsed/refractory multiple myeloma (RRMM) who have failed prior treatment with at least three regimens of different mechanisms of action (an immunomodulatory agent, a proteasome inhibitor, and an anti-CD38 monoclonal antibody), and have confirmed bone marrow plasma cell membrane GPRC5D expression >= 20%. The treatment regimen employs a GPRC5D-targeted chimeric antigen receptor T-cell (CAR-T) therapy (OriCAR-017) administered as a single intravenous infusion. The trial is currently being conducted across 8 domestic core hematology hospitals in China, including The First Affiliated Hospital, Zhejiang University School of Medicine; Shanghai Tongji Hospital; Jiangsu Province Hospital; Union Hospital, Tongji Medical College, Huazhong University of Science and Technology; and Sun Yat-sen University Cancer Center.
An Early Exploratory Clinical Study Evaluating the Safety, Tolerability, and Preliminary Efficacy of BCMA/GPRC5D Dual-Targeted Allogeneic Universal CAR-T Cell Injection (DQ1001) in Patients with Relapsed or Refractory Multiple Myeloma (RRMM)
This clinical study is for patients with relapsed or refractory multiple myeloma (RRMM) who have received at least 3 prior lines of therapy. Eligible participants will receive a single intravenous infusion of a universal CAR-T cell product targeting BCMA/GPRC5D (DQ1001) following lymphodepletion preconditioning with fludarabine and cyclophosphamide. This is a single-center, early exploratory study planning to enroll 10 to 16 participants, aiming to evaluate the safety, tolerability, pharmacokinetic characteristics, and preliminary efficacy of the drug.
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