CD3
CD3 is the switch on every T cell. Bispecific drugs grab it with one arm and the tumour with the other, forcing the T cell to attack.
CD3 is the signalling component of the T-cell receptor complex. All T-cell engagers (blinatumomab, teclistamab, tarlatamab, glofitamab, tebentafusp) use an anti-CD3 arm. Affinity tuning of the CD3 arm is the main lever on cytokine release syndrome.
- Target · the protein and the cell it sits on
- Drug · antibody, small molecule, cell or radioligand
- Effect · signal, damage or kill
In plain words · CD3 is the switch on every T cell. Bispecific drugs grab it with one arm and the tumour with the other, forcing the T cell to attack.
- 1 · What it is
CD3 is the switch on every T cell. Bispecific drugs grab it with one arm and the tumour with the other, forcing the T cell to attack.
- 2 · What goes wrong in cancer
Invariant TCR co-receptor; engagement triggers activation and cytokine release independent of MHC.
- 3 · How drugs use it
14 products aim at CD3: bispecific antibodies. Because it sits on the outside of the cell, it can be reached from the bloodstream: antibodies flag the cell, ADCs deliver a toxin, radioligands deliver radiation, and CAR-T or bispecifics bring a T cell.
Biology
Invariant TCR co-receptor; engagement triggers activation and cytokine release independent of MHC.
- All T cells (effector arm, not a tumour target)
Blinatumomab was the first T-cell engager (2014), and is now given to children and adults with leukaemia even when in remission, because it improves survival.
Tebentafusp's successor: a soluble T-cell receptor that recognises a fragment of PRAME, a protein present in most melanomas and many other cancers, and drags T cells onto the tumour.
Elranatamab is Pfizer's BCMA bispecific, given under the skin every week then every two weeks, for myeloma after four prior lines.
Epcoritamab is an under-the-skin injection that pulls T cells onto lymphoma cells; it is approved for relapsed large B-cell and follicular lymphoma, and moving toward first line.
Glofitamab is a fixed-duration bispecific for large B-cell lymphoma, with OS benefit when combined with chemotherapy.
Linvoseltamab is Regeneron's BCMA bispecific, approved in July 2025 with the highest complete-response rate of the class in its pivotal study.
Mosunetuzumab is a fixed-duration CD20 bispecific approved for follicular lymphoma and studied with polatuzumab in large B-cell lymphoma.
Odronextamab is Regeneron's CD20 bispecific, approved in Europe for lymphoma and in the US for follicular lymphoma after earlier FDA rejections over confirmatory-trial enrolment.
J&J's prostate-specific T-cell engager, notable for very little cytokine release in early trials.
Talquetamab is the first drug against GPRC5D, a second myeloma target used after BCMA therapies stop working; taste and skin side effects are its signature.
The first T-cell engager to improve survival in a common solid tumour, small-cell lung cancer.
The first drug to improve survival in metastatic uveal melanoma, and the first TCR-based bispecific.
Teclistamab was the first off-the-shelf bispecific for multiple myeloma, and is now approved after just one prior line of therapy.
Xaluritamig is Amgen's T-cell engager for prostate cancer, now in two phase 3 trials, aiming to do for prostate cancer what tarlatamab did for small-cell lung cancer.
AALL1731 brings immunotherapy into the front-line treatment of the commonest childhood cancer, in the group of children where most relapses were occurring despite good initial risk. Blinatumomab was approved for this use in 2024 and paediatric protocols worldwide are being amended. Whether it can allow less chemotherapy, and its effect on very low-risk children, are the next questions.
E1910 changed the standard of care for adult B-ALL: immunotherapy is now part of front-line consolidation even for patients with no detectable leukaemia, because MRD-negative by flow cytometry does not mean cured. It also demonstrated that a T-cell engager can improve overall survival in a curative setting. Chemotherapy-light or chemotherapy-free regimens built on blinatumomab and inotuzumab are the next step.
Patients with small-cell lung cancer that has relapsed after chemotherapy now have a drug that works far better than topotecan or lurbinectedin, and it is the first T-cell engager approved for a solid tumour. Treatment requires inpatient monitoring for the first doses because of cytokine release syndrome, which most centres now manage on a short-stay basis. It does not yet apply to first-line treatment, where trials are ongoing.
CD20 x CD3 bispecifics gave patients whose lymphoma has failed CAR-T, or who cannot access it, an effective off-the-shelf treatment that can be started within days. Epcoritamab and glofitamab are now standard third-line options and are moving into earlier lines and combinations. They do not yet replace CAR-T, whose remissions appear more durable.
Elranatamab confirmed that BCMA bispecifics are a class, not a one-off, and its protocol-built dose reduction after response set a precedent for lowering the immunosuppressive burden of T-cell engagers. Patients now have two approved BCMA bispecifics and one against GPRC5D (talquetamab). Choosing between them, and sequencing them with CAR-T, remains guided by availability and toxicity profile rather than head-to-head data.
Teclistamab showed that an off-the-shelf bispecific can approach CAR-T-like response rates in late myeloma, giving patients who cannot wait for or access cell therapy a real option. It also exposed the price: prolonged T-cell engagement causes profound immunosuppression, so infection prophylaxis and immunoglobulin replacement are now routine. Less frequent dosing after response is being adopted to reduce this burden.
Latest papers
topQuery for this target: (TITLE:"CD3" OR ABSTRACT:"CD3" OR TITLE:"CD3E" OR ABSTRACT:"CD3E") AND (cancer OR tumor OR tumour OR oncology OR carcinoma OR lymphoma OR leukemia OR leukaemia OR myeloma OR sarcoma OR melanoma OR glioma). Results are unfiltered search hits about CD3, not a curated reading list.