Targeting the T cell receptor β-chain constant region for immunotherapy of T cell malignancies

Mature T cell cancers are typically aggressive, treatment resistant and associated with poor prognosis. Clinical application of immunotherapeutic approaches has been limited by a lack of target antigens that discriminate malignant from healthy (normal) T cells. Unlike B cell depletion, pan–T cell aplasia is prohibitively toxic. We report a new targeting strategy based on the mutually exclusive expression of T cell receptor β-chain constant domains 1 and 2 (TRBC1 and TRBC2). We identify an antibody with unique TRBC1 specificity and use it to demonstrate that normal and virus-specific T cell populations contain both TRBC1+ and TRBC2+ compartments, whereas malignancies are restricted to only one. As proof of concept for anti-TRBC immunotherapy, we developed anti-TRBC1 chimeric antigen receptor (CAR) T cells, which recognized and killed normal and malignant TRBC1+, but not TRBC2+, T cells in vitro and in a disseminated mouse model of leukemia. Unlike nonselective approaches targeting the entire T cell population, TRBC-targeted immunotherapy could eradicate a T cell malignancy while preserving sufficient normal T cells to maintain cellular immunity

Structure-guided engineering of immunotherapies targeting TRBC1 and TRBC2 in T cell malignancies

Peripheral T cell lymphomas are typically aggressive with a poor prognosis. Unlike other hematologic malignancies, the lack of target antigens to discriminate healthy from malignant cells limits the efficacy of immunotherapeutic approaches. The T cell receptor expresses one of two highly homologous chains [T cell receptor β-chain constant (TRBC) domains 1 and 2] in a mutually exclusive manner, making it a promising target. Here we demonstrate specificity redirection by rational design using structure-guided computational biology to generate a TRBC2-specific antibody (KFN), complementing the antibody previously described by our laboratory with unique TRBC1 specificity (Jovi-1) in targeting broader spectrum of T cell malignancies clonally expressing either of the two chains. This permits generation of paired reagents (chimeric antigen receptor-T cells) specific for TRBC1 and TRBC2, with preclinical evidence to support their efficacy in T cell malignancies

Real-world use of pomalidomide and dexamethasone in double refractory multiple myeloma suggests benefit in renal impairment and adverse genetics:A multi-centre UK experience

Myeloma patients who become refractory to immunomodulatory agents (IMiDs) and bortezomib have poor survival, with limited therapeutic options. Pomalidomide has shown improved survival and good tolerability in this patient cohort in clinical trials, but real world data are scarce. We retrospectively analysed all patients treated with pomalidomide at five UK centres between 2013 and 2016. Of 85 patients identified, 70 had sufficient information for response assessments. Median age was 66 years [40–89], 96·5% were refractory to IMiDs, 72·9% were refractory to both an IMiD and bortezomib and 92·9% were refractory to their last treatment. Of 45 patients with fluorescence in situ hybridization results 64% had adverse risk, 19 patients (22·4%) had an estimated glomerular filtration rate <45 ml/min. Grade ≥3 non‐haematological toxicities occurred in 42·4%, and grade ≥3 neutropenia and thrombocytopenia in 38% and 24% respectively, but only 18·8% had dose reductions. The overall response rate was 52·9%. At a median follow‐up of 13·2 months, median progression‐free survival was 5·2 months [95% confidence interval (CI) 4·150–6·238], and median overall survival was 13·7 months (95% CI 11·775–15·707). No significant difference was seen in response, survival or tolerability by renal function, age or cytogenetic risk. This real‐world data support the results seen in published clinical trials

Anti-CCR9 Chimeric Antigen Receptor T cells for T Cell Acute Lymphoblastic Leukemia

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy of immature T lymphocytes, associated with higher rates of induction failure in comparison to B-ALL. The potent immunotherapeutic approaches applied in B-ALL, which have revolutionized the treatment paradigm, have proven more challenging in T-ALL, largely due to a lack of target antigens expressed on malignant but not healthy T cells. Unlike B cell depletion, T cell aplasia is highly toxic. Here, we demonstrate that the chemokine receptor CCR9 is expressed in >70% of cases of T-ALL, including >85% or relapsed/ refractory disease, and only on a small fraction (<5%) of normal T cells. Using cell line models and patient-derived xenografts, we show chimeric antigen receptor (CAR)-T cells targeting CCR9 are resistant to fratricide and have potent anti-leukemic activity both in vitro and in vivo, even at low target antigen density. We propose anti-CCR9 CAR-T cells could be a highly effective treatment strategy for T-ALL, avoiding T cell aplasia and the need for genome engineering that complicate other approaches

Dual T-cell constant β chain (TRBC)1 and TRBC2 staining for the identification of T-cell neoplasms by flow cytometry

Abstract The diagnosis of leukemic T-cell malignancies is often challenging, due to overlapping features with reactive T-cells and limitations of currently available T-cell clonality assays. Recently developed therapeutic antibodies specific for the mutually exclusive T-cell receptor constant β chain (TRBC)1 and TRBC2 isoforms provide a unique opportunity to assess for TRBC-restriction as a surrogate of clonality in the flow cytometric analysis of T-cell neoplasms. To demonstrate the diagnostic utility of this approach, we studied 164 clinical specimens with (60) or without (104) T-cell neoplasia, in addition to 39 blood samples from healthy donors. Dual TRBC1 and TRBC2 expression was studied within a comprehensive T-cell panel, in a fashion similar to the routine evaluation of kappa and lambda immunoglobulin light chains for the detection of clonal B-cells. Polytypic TRBC expression was demonstrated on total, CD4+ and CD8+ T-cells from all healthy donors; and by intracellular staining on benign T-cell precursors. All neoplastic T-cells were TRBC-restricted, except for 8 cases (13%) lacking TRBC expression. T-cell clones of uncertain significance were identified in 17 samples without T-cell malignancy (13%) and accounted for smaller subsets than neoplastic clones (median: 4.7 vs. 69% of lymphocytes, p < 0.0001). Single staining for TRBC1 produced spurious TRBC1-dim subsets in 24 clinical specimens (15%), all of which resolved with dual TRBC1/2 staining. Assessment of TRBC restriction by flow cytometry provides a rapid diagnostic method to detect clonal T-cells, and to accurately determine the targetable TRBC isoform expressed by T-cell malignancies

Targeting the T cell receptor β-chain constant region for immunotherapy of T cell malignancies

Mature T cell cancers are typically aggressive, treatment resistant and associated with poor prognosis. Clinical application of immunotherapeutic approaches has been limited by a lack of target antigens that discriminate malignant from healthy (normal) T cells. Unlike B cell depletion, pan–T cell aplasia is prohibitively toxic. We report a new targeting strategy based on the mutually exclusive expression of T cell receptor β-chain constant domains 1 and 2 (TRBC1 and TRBC2). We identify an antibody with unique TRBC1 specificity and use it to demonstrate that normal and virus-specific T cell populations contain both TRBC1+ and TRBC2+ compartments, whereas malignancies are restricted to only one. As proof of concept for anti-TRBC immunotherapy, we developed anti-TRBC1 chimeric antigen receptor (CAR) T cells, which recognized and killed normal and malignant TRBC1+, but not TRBC2+, T cells in vitro and in a disseminated mouse model of leukemia. Unlike nonselective approaches targeting the entire T cell population, TRBC-targeted immunotherapy could eradicate a T cell malignancy while preserving sufficient normal T cells to maintain cellular immunity