Why CD38, BCMA, and CD3 Are the Core Targets in Myeloma Immunotherapy

Multiple myeloma is a clonal plasma cell malignancy accounting for approximately 1% of all cancers and more than 10% of hematologic malignancies, with a median diagnosis age of approximately 61 years. Three molecular targets dominate the therapeutic design landscape in this disease: CD38, BCMA, and CD3 — each selected for properties that make them unusually tractable for antibody-based immune engagement.

CD38 is a multifunctional transmembrane glycoprotein expressed at high and homogeneous density on malignant plasma cells while present at relatively low levels on normal lymphoid and myeloid cells. Its pleiotropic role — as an ectoenzyme catalyzing NAD⁺ conversion to immunosuppressive adenosine, as an adhesion molecule interacting with CD31, and as a receptor — makes it an unusually tractable therapeutic target. As one retrieved paper states, “the very high and homogeneous expression of CD38 on myeloma PCs makes it an attractive target for novel therapeutic strategies.” Daratumumab and isatuximab are established clinical agents, with daratumumab described in retrieved literature as “part of standard treatment regimens of both newly diagnosed as well as relapsed/refractory MM patients.”

BCMA (B-cell maturation antigen; TNFRSF17) is universally expressed on normal and neoplastic plasma cells but absent from most non-hematopoietic tissues, providing high tumor selectivity. BAFF and APRIL serve as its proliferation ligands in the bone marrow microenvironment, and soluble BCMA levels in serum correlate with tumor burden and predict progression-free and overall survival. Retrieved patent filings from Janssen Biotech, Regeneron Pharmaceuticals, EngMab SARL, Bristol-Myers Squibb, and Novartis AG all claim BCMA as a primary tumor-associated antigen in bispecific and trispecific constructs.

A notable challenge specific to BCMA is soluble BCMA shedding from the tumor cell surface, which may act as a decoy and reduce effective bispecific binding — a challenge not explicitly addressed in the trispecific patent literature retrieved. This shedding mechanism, combined with CD38 downregulation documented as a resistance mechanism to anti-CD38 monoclonal antibodies, underscores why single-target approaches face inherent limitations in the relapsed/refractory setting, according to NIH-indexed literature on antigen escape.

The Bispecific T-Cell Engager Landscape: Clinical Signals and Resistance Gaps

Bispecific T-cell engagers (TCEs) targeting BCMA × CD3 represent the dominant modality in the retrieved dataset, with early-phase clinical response rates of 61–83% in the most active dose cohorts against heavily pretreated multiple myeloma. These molecules form a cytolytic immunological synapse by simultaneously binding BCMA on malignant plasma cells and CD3ε on T cells, triggering granzyme and perforin release and tumor cell lysis. Despite these response rates, retrieved academic reviews consistently identify T-cell exhaustion, antigen downregulation, and tumor immune escape as the primary resistance mechanisms that limit durability of response.

A distinct bispecific modality targets CD38 rather than BCMA for T-cell redirection. ISB 1342, developed by Ichnos Sciences using the BEAT® platform, is a preclinical-stage CD38 × CD3 bispecific designed specifically for patients with reduced daratumumab sensitivity. It binds CD38 at a non-competing epitope and demonstrates in vitro killing of MM cell lines with varying CD38 expression levels, with in vivo activity exceeding that of daratumumab across multiple modes of action.

“Combining CD2- and TCR complex-engagement in a single multispecific molecule can stimulate both a primary signaling pathway that promotes T-cell mediated lysis of tumor cells… and a second co-stimulatory pathway to induce T-cell proliferation and potentially overcome anergy.”

An orthogonal innate immune approach is represented by ISB 1442 — Ichnos Sciences’ CD38 × CD47 “2+1 biparatopic” bispecific, which uses two CD38-binding Fab arms targeting distinct epitopes and a single anti-CD47 Fab arm blocking the CD47–SIRPα “don’t eat me” interaction on phagocytes. Unlike T-cell engagers, this molecule targets macrophages, monocytes, and dendritic cells, and its Fc is engineered to enhance antibody-dependent cellular phagocytosis (ADCP). This approach avoids direct T-cell engagement and associated CRS, representing a potentially important strategy for post-daratumumab relapsed/refractory MM, as documented by research from WIPO-registered patent families in this space.

The hemibody concept from University Clinic Würzburg represents yet another mechanistic approach: complementary antibody fragment pairs that redirect T cells only upon dual antigen co-expression, combining CD38 and SLAMF7 targeting. Retrieved results indicate hemibodies spare single-antigen-positive bystanders while eliminating dual-positive MM cells, and avoid the massive CRS and T-cell fratricide associated with single-target BiTEs in both in vitro and in vivo models — an important safety design principle for next-generation MM T-cell engagers.

Trispecific Architectures: Co-stimulation as the Key Differentiator

Trispecific binding molecules represent the most forward-looking modality in the retrieved dataset, predominantly represented by patent filings and one quantitative systems pharmacology modeling study. Two distinct structural strategies are documented, each targeting a different co-stimulatory mechanism to address the T-cell exhaustion that limits bispecific TCE durability.

Novartis: BCMA × CD3 × CD2 — Overcoming T-Cell Anergy

Novartis AG has filed patents across multiple jurisdictions (IL, WO, CA, AU) describing trispecific binding molecules (TBMs) that engage BCMA as the primary tumor target, CD3 for T-cell activation, and CD2 for co-stimulation. The co-stimulatory rationale is explicit in the patent text: CD2 engagement is described as a mechanism to “induce T-cell proliferation and potentially overcome anergy” — directly addressing the T-cell exhaustion resistance mechanism documented in retrieved bispecific literature. The Novartis patent family also contemplates a variant in which a second tumor-associated antigen replaces CD2, broadening tumor-targeting coverage. This patent portfolio represents the most direct IP signal for the trispecific format in multiple myeloma in the retrieved dataset.

Sanofi: CD38 × CD3 × CD28 — Dual Co-stimulatory and Tumor-Targeting Arm

Retrieved academic literature from Sanofi describes a quantitative systems pharmacology (QSP) modeling study characterizing a trispecific TCE binding CD3 on T cells, CD38 on tumor cells, and CD28 as both a T-cell co-stimulatory signal and an additional tumor-associated target. CD28 is described as overexpressed on MM cells, giving the third arm a dual function: amplifying T-cell activation and providing additional tumor targeting. The model demonstrates that the CD28 co-stimulatory arm enhances T-cell activation, proliferation, and cytolytic activity beyond what a bispecific CD38 × CD3 engager alone achieves — a mechanistic rationale for the trispecific format that is supported by computational-experimental validation, though no clinical data has been retrieved for this molecule.

The Phase I clinical data for BM38 — a bispecific CAR-T cell therapy targeting both BCMA and CD38 — provides the only human proof-of-concept in the retrieved dataset for dual-target BCMA + CD38 therapy. In 23 patients with relapsed/refractory MM, BM38 CAR-Ts showed superior in vitro cytotoxicity against heterogeneous MM cells compared to single-target BCMA or CD38 CARs alone. CRS occurred in 87% of patients (20/23), with 65% experiencing grade 1–2 events. Neurotoxicity was not observed. While CAR-T and antibody modalities are mechanistically distinct, this data may de-risk the dual-target rationale for trispecific antibody designs incorporating both antigens, a principle supported by research indexed by EPO patent examiners in this technology class.

Patent Assignee Landscape: Who Owns the IP and Where the White Space Lies

Innovation activity in the CD38/BCMA/CD3 space spans large pharmaceutical companies, biotechs, and academic institutions, with a clear predominance of patent-driven commercial activity for T-cell engaging formats. Genmab A/S is the most patent-prolific entity in the retrieved dataset for CD38 targeting, with at least 10 retrieved patent records across IL, EP, SG, and HU jurisdictions covering foundational anti-CD38 human monoclonal antibodies. Critically, most of these are now designated inactive in the retrieved records — signaling expiring or lapsed protection that may open opportunities for biosimilar development and next-generation engineering.

Janssen Biotech holds multiple active IL patents covering anti-BCMA antibodies, bispecific BCMA × CD3 binding molecules, anti-CD38 combination therapies (including combination with all-trans retinoic acid to upregulate CD38 surface density and restore sensitivity), and anti-CD38 antibodies for AML. Regeneron Pharmaceuticals holds patents in IL, SG, and EP jurisdictions, with an active EP patent dated as recently as January 2025, suggesting continued prosecution activity. EngMab SARL and Bristol-Myers Squibb hold patents explicitly claiming combination of a BCMA × CD3 bispecific with an anti-CD38 antibody — the closest precedent in the dataset to a CD38 × BCMA × CD3 trispecific strategy, but structured as a drug combination rather than a single molecule.

Shanghai EpiMab Biotherapeutics holds multiple IL patents (pending) covering the FIT-Ig (Fabs-in-Tandem Immunoglobulin) format for BCMA × CD3, which claims to incorporate anti-CD3 and anti-BCMA binding sites without significant loss of affinity — representing emerging Chinese biotech IP in the MM T-cell engager space. Academic institutions including University Clinic Würzburg, VU University Amsterdam/Amsterdam UMC, Harvard Medical School/Dana-Farber, University Medical Center Hamburg-Eppendorf, and Sanofi contribute predominantly through literature rather than patent filings, consistent with their mechanistic and resistance-focused research orientation, as catalogued by OECD innovation mapping frameworks for biopharmaceutical R&D.

Strategic Implications for Drug Developers and IP Teams

The retrieved patent and literature dataset reveals five actionable signals for organizations developing next-generation multiple myeloma immunotherapies. Each addresses a distinct dimension of the competitive and scientific landscape as it currently stands in the retrieved data.

1. CD38 × BCMA × CD3 as a Single Molecule Remains Unclaimed

The specific three-target CD38 × BCMA × CD3 trispecific format as a single integrated molecule has not been explicitly claimed in the retrieved patent dataset. Novartis claims BCMA × CD3 × CD2 and Sanofi models CD38 × CD3 × CD28, but the CD38 × BCMA × CD3 combination remains a potential white-space opportunity. The EngMab/BMS combination patents represent the closest precedent but are structured as a drug combination rather than a single molecule. Patent applicants should conduct thorough freedom-to-operate analysis given the complex layering of combination-use and formulation patents still in active status.

2. Co-stimulatory Arm Engineering Is the Primary Differentiation Strategy

CD28 and CD2 co-stimulation integrated into the trispecific architecture is emerging as the mechanistic solution to T-cell exhaustion, which retrieved literature identifies as a primary resistance mechanism against bispecific TCEs in MM. The Novartis BCMA × CD3 × CD2 approach eliminates the need for combination with a separate checkpoint inhibitor by integrating anergy override directly into the molecule. The Sanofi CD38 × CD3 × CD28 approach uniquely exploits CD28’s dual role as a T-cell co-stimulator and MM surface antigen. Patent filers and drug developers should prioritize co-stimulatory arm engineering as a differentiation strategy over adding a third tumor-associated antigen alone.

3. Genmab’s Foundational IP Expiry Creates Engineering Opportunity

Genmab’s foundational CD38 antibody patents are predominantly designated inactive or inactive-status in retrieved records. This may create freedom-to-operate for next-generation CD38-containing bispecifics or trispecifics. However, developers should conduct thorough FTO analysis given the complex layering of combination-use and formulation patents from MorphoSys and Janssen that remain in active status in the retrieved dataset.

4. BM38 Phase I Data De-risks the Dual-Target Rationale

The bispecific BCMA × CD38 CAR-T Phase I clinical data (BM38, Zhejiang Cellyan, 23 patients) provides the only human proof-of-concept in the retrieved dataset for dual-target BCMA + CD38 therapy, with a manageable CRS profile: 87% incidence, 65% grade 1–2, and no observed neurotoxicity. While CAR-T and antibody modalities are mechanistically distinct, this data may de-risk the dual-target rationale for trispecific antibody designs incorporating both antigens.

5. QSP Modeling Is an Essential IND-Enabling Tool for Trispecifics

Computational quantitative systems pharmacology modeling, as employed by Sanofi for their CD38 × CD3 × CD28 trispecific, is emerging as an essential IND-enabling tool for multispecific molecules with complex dose-response relationships across three binding partners. Academic researchers and drug developers should integrate QSP/mechanistic PK-PD modeling early in trispecific development programs to optimize dose regimens and predict CRS risk before first-in-human studies, consistent with regulatory guidance from FDA on model-informed drug development for complex biologics.

“The specific three-target CD38 × BCMA × CD3 trispecific format as a single integrated molecule has not yet been explicitly claimed in the retrieved patent dataset — representing a potential white-space opportunity for next-generation myeloma drug developers.”