CD4+ CAR-T cell exhaustion associated with early relapse of multiple myeloma after BCMA CAR-T cell therapy

Multiple myeloma is characterized by frequent clinical relapses following conventional therapy. Recently, chimeric antigen receptor T (CAR-T) cells targeting B-cell maturation antigen (BCMA) has been established as a treatment option for patients with relapsed or refractory disease. However, while >70% of patients initially respond to this treatment, clinical relapse and disease progression occur in most cases. Recent studies showed persistent expression of BCMA at the time of relapse, indicating that immune intrinsic mechanisms may contribute to this resistance. While there were no pre-existing T cell features associated with clinical outcomes, we found that patients with a durable response to CAR-T cell treatment had greater persistence of their CAR-T cells compared to patients with transient clinical responses. They also possessed a significantly higher proportion of CD8+ T effector memory cells. In contrast, patients with short-lived responses to treatment have increased frequencies of cytotoxic CD4+ CAR-T cells. These cells expand in vivo early after infusion but express exhaustion markers (HAVCR2 and TIGIT) and remain polyclonal. Finally, we demonstrate that non-classical monocytes are enriched in the myeloma niche and may induce CAR-T cell dysfunction through mechanisms that include TGFβ. These findings shed new light on the role of cytotoxic CD4+ T cells in disease progression after CAR-T cell therapy.

Neoadjuvant CD40 Agonism Remodels the Tumor Immune Microenvironment in Locally Advanced Esophageal/Gastroesophageal Junction Cancer

Sotigalimab is an agonistic anti-CD40 mAb that can modulate antitumor immune responses. In a phase II clinical trial of sotigalimab combined with neoadjuvant chemoradiation (CRT) in locally advanced esophageal/gastroesophageal junction (E/GEJ) cancer with the primary outcome of efficacy as measured by pathologic complete response (pCR) rate, the combination induced pCR in 38% of treated patients. We investigated the mechanism of action of sotigalimab in samples obtained from this clinical trial. Tumor biopsies and peripheral blood samples were collected at baseline, following an initial dose of sotigalimab, and at the time of surgery after CRT completion from six patients. High dimensional single-cell techniques were used, including combined single-cell RNA-sequencing and proteomics (CITEseq) and multiplexed ion beam imaging, to analyze immune responses. Sotigalimab dramatically remodeled the immune compartment in the periphery and within the tumor microenvironment (TME), increasing expression of molecules related to antigen processing and presentation and altering metabolic pathways in myeloid cells. Concomitant with these changes in myeloid cells, sotigalimab treatment primed new T cell clonotypes and increased the density and activation of T cells with enhanced cytotoxic function. Sotigalimab treatment also induced a decrease in the frequency of Tregs in the TME. These findings indicate that a single dose of sotigalimab leads to enhanced antigen presentation that can activate T cells and induce new T cell clones. This restructuring of the TME provides elements which are critical to the development of effective antitumor immune responses and improved clinical outcomes.

Use of high-dimensional and spatial immune profiling to explore sotigalimab (CD40 agonist) activation of antigen presenting cells and T cells in the tumor microenvironment in patients with esophageal/gastroesophageal junction cancer

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Background: Neoadjuvant chemoradiation (CRT) followed by surgical resection is standard of care for patients with locally advanced esophageal/gastroesophageal junction (E/GEJ) cancer. A pathologic complete response (pCR) at surgery is associated with improved survival outcomes. Sotigalimab (sotiga) is a potent CD40 agonist mAb capable of inducing and expanding anti-tumor immune responses. A recently reported non-randomized phase II clinical trial of sotiga combined with CRT in E/GEJ cancer patients showed promising pCR rates that compared favorably to historical data1. Here, deep immune profiling was performed on a subset of patients to gain insight into the mechanism of sotiga. Methods: In the initial safety cohort (n=6) of this phase II E/GEJ clinical trial, tumor and blood samples were obtained pre-treatment and again following a single lead-in dose of sotiga, prior to initiation of CRT. Immune modulation in the tumor microenvironment and blood of patients was examined using high dimensional techniques, including mass cytometry, multiplexed ion beam imaging, and single cell RNA sequencing. Results: Sotiga administration dramatically re-models the tumor microenvironment, inducing immune infiltration and shifting the immune composition predominantly toward an inflammatory phenotype. At baseline, E/GEJ tumors were infiltrated with myeloid cells and T cells, the majority of which were Tregs. Sotiga increased antigen-presenting cell (APC) infiltration in tumors and activated dendritic cells as demonstrated by expression of MHCII and CD86. Sotiga treatment also induced infiltration of activated cytotoxic T cells and decreased the proportion of Tregs. There was also evidence of T cell activation in peripheral blood with increased expression of 4-1BB, CTLA-4, ICOS and PD-L1. Therapeutic responses to sotiga were associated with distinct T cell signatures both at baseline and on-treatment. At baseline, pCR patients (representing 4 of the 6 pts (67%) in this cohort) had a higher ratio of memory CD4+ T cells to Tregs which further increased following sotiga treatment, whereas patients who did not have a pCR had a higher proportion of myeloid cells at baseline and did not show a decrease in Treg cells after sotiga treatment. Conclusions: Sotiga induced dramatic changes in the tumor microenvironment including increased frequency of activated T cells and APCs, and decreased frequency of Tregs. A distinct signature of T cell infiltration in baseline tumor biopsies was observed in patients who achieved a pCR versus those who did not, potentially identifying patients that may benefit from this novel treatment strategy.

Attenuating CD3 affinity in a PSMAxCD3 bispecific antibody enables killing of prostate tumor cells with reduced cytokine release

BACKGROUND

Therapeutic options currently available for metastatic castration-resistant prostate cancer (mCRPC) do not extend median overall survival >6 months. Therefore, the development of novel and effective therapies for mCRPC represents an urgent medical need. T cell engagers (TCEs) have emerged as a promising approach for the treatment of mCRPC due to their targeted mechanism of action. However, challenges remain in the clinic due to the limited efficacy of TCEs observed thus far in solid tumors as well as the toxicities associated with cytokine release syndrome (CRS) due to the usage of high-affinity anti-CD3 moieties such as OKT3.

METHODS

Using genetically engineered transgenic rats (UniRat and OmniFlic) that express fully human IgG antibodies together with an NGS-based antibody discovery pipeline, we developed TNB-585, an anti-CD3xPSMA TCE for the treatment of mCRPC. TNB-585 pairs a tumor-targeting anti-PSMA arm together with a unique, low-affinity anti-CD3 arm in bispecific format. We tested TNB-585 in T cell-redirected cytotoxicity assays against PSMA+ tumor cells in both two-dimensional (2D) cultures and three-dimensional (3D) spheroids as well as against patient-derived prostate tumor cells. Cytokines were measured in culture supernatants to assess the ability of TNB-585 to induce tumor killing with low cytokine release. TNB-585-mediated T cell activation, proliferation, and cytotoxic granule formation were measured to investigate the mechanism of action. Additionally, TNB-585 efficacy was evaluated in vivo against C4-2 tumor-bearing NCG mice.

RESULTS

In vitro, TNB-585 induced activation and proliferation of human T cells resulting in the killing of PSMA+ prostate tumor cells in both 2D cultures and 3D spheroids with minimal cytokine release and reduced regulatory T cell activation compared with a positive control antibody that contains the same anti-PSMA arm but a higher affinity anti-CD3 arm (comparable with OKT3). In addition, TNB-585 demonstrated potent efficacy against patient-derived prostate tumors ex vivo and induced immune cell infiltration and dose-dependent tumor regression in vivo.

CONCLUSIONS

Our data suggest that TNB-585, with its low-affinity anti-CD3, may be efficacious while inducing a lower incidence and severity of CRS in patients with prostate cancer compared with TCEs that incorporate high-affinity anti-CD3 domains.

Effect of modulation of CD3 binding in a PSMAxCD3 T-cell engaging bispecific antibody on maintenance of efficient tumor cell kill and cytokine release

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Background: Castration resistant prostate cancer (CRPC) is an incurable disease and represents a significant unmet need. Prostate specific membrane antigen (PSMA) is a protein highly expressed on the surface of prostate cancer cells; expression has been shown to increase with disease progression. Therapies targeting PSMA, such as anti-PSMA radioligand conjugates, have shown promise in clinical trials, validating this target for CRPC. T-cell recruiting bispecific antibodies (T-BsAbs) have demonstrated potent tumor killing activity against multiple tumor types, but immune-mediated toxicities have hampered T-cell redirecting therapies to date. Using Teneobio’s unique antibody discovery platform, we have developed a CD3xPSMA bispecific antibody (TNB-585) that retains the potent cytotoxicity of other T-BsAbs but with significantly reduced cytokine release. Methods: Antibodies targeting CD3 and PSMA were generated via immunization of our proprietary transgenic animals. Candidate antibodies were selected by repertoire deep sequencing of B-cells from draining lymph nodes, followed by high-throughput gene assembly and recombinant expression. Multiple bispecific antibodies targeting CD3 and PSMA were assembled and evaluated for their ability to selectively activate primary human T-cells and mediate killing of PSMA+ tumor cells in vitro, ex vivo, and in vivo. T-cell activation surface markers, cytokine production, and tumor cell cytotoxicity were measured. Results: In co-culture experiments, primary human T-cells were activated only in the presence of both the bispecifics and PSMA+ cells. These bispecifics mediated potent and selective cytotoxicity against PSMA-positive tumor cells, prostate tumor cell lines, or primary human prostate tumor cells isolated from patients. From among these we identified TNB-585, which showed attenuated binding to CD3. TNB-585 mediated comparable tumor cell cytotoxicity to CD3xPSMA T-BsAbs containing a high affinity anti-CD3 domain but with significantly reduced cytokine production. TNB-585 also showed tumor growth inhibition in xenograft models of prostate cancer in vivo. Conclusions: We have developed a novel CD3xPSMA T-BsAb that mediates T-cell killing of PSMA+ tumor cells with minimal production of cytokines. This molecule may improve safety, efficacy, and offer opportunities for combination therapy to treat CRPC. A Phase 1 clinical trial of this compound in CRPC is scheduled to begin in Q1 2021.