Solid organ transplantation: solid but not yet spectacular

Journal of Clinical Investigation · 2024-01-01 · 1 citations

Harnessing regulatory T cells to establish immune tolerance

Science Translational Medicine · 2024-03-13 · 49 citations

Engineered regulatory T (T reg ) cells have emerged as precision therapeutics aimed at inducing immune tolerance while reducing the risks associated with generalized immunosuppression. This Viewpoint highlights the opportunities and challenges for engineered T reg cell therapies in treating autoimmune and other inflammatory diseases.

Donor antigen-specific regulatory T cell administration to recipients of live donor kidneys: A ONE Study consortium pilot trial

American Journal of Transplantation · 2023-07-07 · 29 citations

Abstract CT187: Phase 1 Trial of RTX-240, allogeneic red blood cells engineered to express 4-1BBL and trans-presented IL-15, in patients (Pts) with advanced solid tumors

Cancer Research · 2022-06-15 · 3 citations

Abstract Background: RTX-240 is an allogeneic cellular therapy genetically engineered to express high copy numbers of trimeric 4-1BBL and IL-15/IL-15Rα fusion proteins on the RBC surface membrane. RTX-240 is designed to activate and expand CD8+ memory T cells and NK cells and is restricted to the normal biodistribution of red blood cells to mitigate toxicity. Safety, pharmacodynamic (PD) effects, pharmacokinetics (PK) and preliminary efficacy of RTX-240 were assessed in a Phase 1 study of pts with solid tumors. Methods: Pts with relapsed/refractory solid tumors not eligible for standard therapy were treated with monotherapy RTX-240 in 10 cohorts utilizing 6 dose levels (1x108-5x1010 cells per dose) and 4 different schedules until disease progression or unacceptable toxicity. Peripheral blood and tumor tissue were collected at baseline and on-treatment. Results: As of Dec 3, 2021, 30 pts with solid tumors (median age 58 yr, range 23-80, 17 males, 20 ECOG 1), were treated with single agent RTX-240. Pts had previously received a median of 3 therapies (range, 1-9); 21 pts had received prior PD-1/PD-L1 inhibitor (i) therapy. Common tumor types included NSCLC (n=7), melanoma (n=7), colorectal/lower GI (n=4) and RCC (n=3). Per RECIST v1.1, a confirmed partial response (PR) was observed in 1 pt with anal carcinoma and an unconfirmed PR in a uveal melanoma, both of whom had been previously treated with a PD-1. Disease control (PR or stable disease > 12 weeks) occurred in 11/30 pts (37%), of which 7 had received a prior PD-1 for a median of 8 months. Peripheral blood PD studies demonstrate activation, expansion, and cytotoxic potential (GzB) of both NK and memory CD8+ T cells. Every pt with evaluable samples (n=29) had an increase in at least one of the activation or expansion parameters, and the majority had an increase in all. There was also a clear dose response effect in NK cell numbers and trends in other PD markers. Immune activation was observed by increases in plasma IFN-γ in a subset of patients. On-treatment biopsies in a subset (3/5) of evaluable pts show infiltration of NK and/or T cells into the tumor microenvironment (TME) after RTX-240 dosing. No DLTs or related grade (Gr)>3 AEs were seen. The most common treatment-related AEs (Gr 1-2) were fatigue (n = 6); chills, nausea, decrease in appetite, arthralgia (n =3); and fever, myalgia, dysgeusia, and hyperhidrosis (n=2). Additional Gr 2 irAEs include pneumonitis, adrenal insufficiency, hypothyroidism, and worsening transaminitis. Conclusions: RTX-240 is well tolerated at all tested doses, schedules and routes. The drug leads to activation, expansion and trafficking of two target cells (memory CD8+ T cells and NK cells) into the TME, exhibits a clear dose response effect with NK cells and demonstrates preliminary evidence of anti-tumor activity. Dose escalation continues and a PD-1 inhibitor combination arm is also enrolling. Citation Format: Omid Hamid, Melissa L. Johnson, Jason Luke, Richard T. Maziarz, Jamie Merchan, Emerson E. Lim, Sandip P. Patel, Geoffrey M. Kuesters, Iga Sienczylo, Gilad Gordon, Karen Campbell, Kristin Horton, Laurence Turka, Alexander I. Spira. Phase 1 Trial of RTX-240, allogeneic red blood cells engineered to express 4-1BBL and trans-presented IL-15, in patients (Pts) with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT187.

A phase 1/2 study of RTX-224, an engineered red blood cell expressing 4-1BB ligand and membrane-bound IL-12, for the treatment of patients with select advanced solid tumors.

Journal of Clinical Oncology · 2022-06-01 · 2 citations

TPS2680 Background: RTX-224 is a genetically engineered off-the-shelf, allogeneic red blood cell that expresses the costimulatory molecule 4-1BB ligand (4-1BBL) and cytokine interleukin-12 (IL-12) on the cell surface. The use of 4-1BB and IL-12 agonists for cancer immunotherapy has been limited due to systemic toxicities. Unlike agonist antibodies and recombinant cytokines, which are distributed systemically, Red Cell Therapeutics, such as RTX-224, are restricted to the vasculature and spleen, which may limit toxicities previously observed with agonist 4-1BB monoclonal antibodies and recombinant IL-12. RTX-224 is designed to be a broad immune agonist of both adaptive and innate responses that activates and expands effector and memory CD8+ and CD4+ T cells, cytotoxic natural killer (NK) cells and produces inflammatory cytokines and chemokines, leading to enhanced antigen presentation. In preclinical studies, the combined activation of both adaptive and innate immune responses by the murine surrogate of RTX-224 led to antitumor activity while the restricted biodistribution improved the safety profile. Methods: The RTX-224-01 study is a Phase 1/2, first-in-human, multi-center, dose-escalation and expansion study of RTX-224 in patients with relapsed or refractory urothelial cancer, squamous cell carcinoma of the head and neck, non-small cell lung cancer, triple negative breast cancer and cutaneous melanoma. Safety, tolerability, pharmacokinetics and pharmacodynamics and anti-tumor activity of RTX-224 will be assessed. Approximately 28 patients will be enrolled across dose level cohorts to identify the recommended Phase 2 dose (RP2D). The starting dose is 100 million (1x10 8 ) cells administered intravenously every 3 weeks (Q3W) and the dose will be escalated by half-log increments following a Bayesian logarithmic regression model (BLRM) with overdose control. Following RP2D selection, each of the 5 expansion cohorts will enroll approximately 20 patients. Pharmacodynamic and exploratory biomarker studies correlative to clinical response will be evaluated on peripheral blood and paired tumor biopsies. Multiple technologies will be employed to profile the innate and adaptive responses following RTX-224 treatment. The study is open and enrolling patients in Phase 1. Clinical trial information: NCT05219578.

208 RTX-224, an engineered allogeneic red cell therapeutic expressing 4–1BBL and IL-12, activates immune cells in blood and spleen to promote tumor growth inhibition in mice

Regular and Young Investigator Award Abstracts · 2021-11-01 · 2 citations

<h3>Background</h3> Agonist antibodies and recombinant cytokines have had limited success in the clinic due to three factors: severe toxicity leading to a narrow therapeutic index, the diminished activity of an agonistic antibody compared with natural ligand, and the lack of multiple signals needed to effectively activate most cell types. To address these limitations, Rubius Therapeutics has developed RTX-224, an allogeneic red cell therapeutic genetically engineered to express hundreds of thousands of copies of 4-1BBL and IL-12 in their natural conformation on the cell surface. RTX-224 is designed to activate four key target cell types: CD4+ and CD8+ T cells, antigen presenting cells and NK cells for a broad and effective anti-tumor response while providing improved safety due to the restricted biodistribution of red blood cells to the vasculature and spleen. Here we investigated the potential efficacy and mechanism of action of RTX-224 using the mouse surrogate mRBC-224. <h3>Methods</h3> mRBC-224 was administered intravenously (i.v.) to normal or tumor-bearing mice (B16F10 tumor models). Blood, spleen and tumors were harvested and the pharmacodynamic effects of mRBC-224 on immune cells were evaluated. <h3>Results</h3> mRBC-224 administered to mice inoculated i.v. with B16F10 melanoma reduced the number of metastases (p&lt;0.0001 and 76.8% tumor growth inhibition on Day 14). This was accompanied by increased proliferation (Ki67+) and cytotoxicity (GzmB+) of tumor-infiltrating CD8+ T cells and NK cells, and an increased CD8+ effector memory (TEM) phenotype. Similarly, mRBC-224 reduced tumor growth in the B16F10 s.c. model (p&lt;0.0001 and 56.2% tumor growth inhibition on Day 9), and this was associated with increased frequency of activated (MHC-II+) tumor-infiltrating macrophages. Consistent with the known biodistribution of red cells, mRBC-224 did not distribute to the tumor but was predominantly localized in the blood and spleen raising the question about mRBC-224 mechanism of action in mediating antitumor responses. In normal and B16F10 s.c. tumor-bearing mice, mRBC-224 induced the activation of CD8+ T cells, NK cells and monocytes/macrophages in blood and spleen in a dose-dependent manner. PD studies in the tumor suggest that these activated immune cells are capable of trafficking from blood/spleen to the tumor. These results align with published data suggesting that activated T cells in the spleen or blood can replenish exhausted tumor-infiltrating cells. <h3>Conclusions</h3> Taken together, these data unveil the mechanism of action of mRBC-224 and suggest that mRBC-224 activate immune cells in the spleen and blood, leading to their trafficking into the tumor microenvironment to promote efficacy.

Ex vivo generation of regulatory T cells from liver transplant recipients using costimulation blockade

American Journal of Transplantation · 2021-09-16 · 11 citations

Abstract PO044: RTX-321, an allogeneic red blood cell-based artificial antigen presenting cell, expressing MHC I-peptide, 4-1BBL and IL-12, engages primary human HPV-specific T cells and boosts other general immune responses

Cancer Immunology Research · 2021-02-01 · 2 citations

Abstract The high-risk human papillomavirus (HPV) strain 16 accounts for ~ 70% of all cervical cancers and 80% of head and neck cancers associated with HPV infection., Despite available therapies, there remains a critical need for new treatment options for advanced HPV 16-associated cancers. To address this, we have genetically engineered red blood cells to create an allogeneic artificial antigen presenting cell (APC), RTX-321, that expresses an HPV E7 peptide bound to MHC I (HLA-A*02:01), 4-1BBL and IL-12 on the cell surface to mimic the biology of T cell APC interactions. RTX-321 is designed to enhance both the quantity and quality of endogenous tumor-specific T cells. In this study, we evaluated the mechanisms through which RTX-321 promotes anti-tumor immune responses, particularly its ability to engage and activate HPV 16-specific CD8+ T cells in the context of mixed immune populations in peripheral blood mononuclear cells (PBMCs) and to modulate other key immune cell types in PBMCs. Primary CD8+ T cells were engineered to express the HPV E7 TCR, resulting in HPV E7-specific CD8+ T cells (E7 TCR-T). To determine whether RTX-321’s immune modulatory activities are dependent on the presence of antigen-specific T cells, we examined the effect of RTX-321 on PMBCs admixed with E7 TCR-T as compared to PBMCs alone. RTX-321 selectively expanded HPV E7-specific CD8+ T cells from the PBMC mixture in a dose-dependent manner. RTX-321 preferentially upregulated activation markers and effector molecules, and promoted effector memory on HPV E7-specific CD8+ T cells, compared to HPV independent CD8+ T cells. In addition to these HPV antigen-specific responses, modulations on other immune cells were observed with RTX-321 treatment. RTX-321 induced activation marker upregulation on general CD8+ T cells, as well as NK cell expansion, activation and effector molecule upregulation, independent of the presence of E7 TCR-T. In PBMCs, RTX-321 increased proinflammatory cytokine and chemokine secretion, including IFNγ, TNFα and CXCL10. The addition of E7 TCR-T cells further increased the production of IFNγ and TNFα in PBMCs, suggesting its potential role in further promoting the immune response by secreting effector molecules. Overall, our data indicate that RTX-321 not only engages HPV 16 antigen-specific CD8+ T cells, but also other key immune cell populations of the adaptive and innate immune systems to promote a broad and robust anti-tumor response. An Investigational New Drug application for RTX-321 for the treatment of patients with HPV 16-positive solid tumors is planned by the end of 2020. Citation Format: Mengyao Luo, Shamael S. Dastagir, Xuqing Zhang, Andrea Schmidt, Beatriz Marques, Timothy J. Lyford, Billy Blanco, Laurence A. Turka, Thomas J. Wickham, Tiffany F. Chen. RTX-321, an allogeneic red blood cell-based artificial antigen presenting cell, expressing MHC I-peptide, 4-1BBL and IL-12, engages primary human HPV-specific T cells and boosts other general immune responses [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO044.

Engineered red blood cells as an off-the-shelf allogeneic anti-tumor therapeutic

Nature Communications · 2021-05-11 · 58 citations

Abstract Checkpoint inhibitors and T-cell therapies have highlighted the critical role of T cells in anti-cancer immunity. However, limitations associated with these treatments drive the need for alternative approaches. Here, we engineer red blood cells into artificial antigen-presenting cells (aAPCs) presenting a peptide bound to the major histocompatibility complex I, the costimulatory ligand 4-1BBL, and interleukin (IL)-12. This leads to robust, antigen-specific T-cell expansion, memory formation, additional immune activation, tumor control, and antigen spreading in tumor models in vivo. The presence of 4-1BBL and IL-12 induces minimal toxicities due to restriction to the vasculature and spleen. The allogeneic aAPC, RTX-321, comprised of human leukocyte antigen-A*02:01 presenting the human papilloma virus (HPV) peptide HPV16 E7 11-19 , 4-1BBL, and IL-12 on the surface, activates HPV-specific T cells and promotes effector function in vitro. Thus, RTX-321 is a potential ‘off-the-shelf’ in vivo cellular immunotherapy for treating HPV + cancers, including cervical and head/neck cancers.

Anti-tumor effects of RTX-240: an engineered red blood cell expressing 4-1BB ligand and interleukin-15

Cancer Immunology Immunotherapy · 2021-07-09 · 20 citations

Recombinant agonists that activate co-stimulatory and cytokine receptors have shown limited clinical anticancer utility, potentially due to narrow therapeutic windows, the need for coordinated activation of co-stimulatory and cytokine pathways and the failure of agonistic antibodies to recapitulate signaling by endogenous ligands. RTX-240 is a genetically engineered red blood cell expressing 4-1BBL and IL-15/IL-15Rα fusion (IL-15TP). RTX-240 is designed to potently and simultaneously stimulate the 4-1BB and IL-15 pathways, thereby activating and expanding T cells and NK cells, while potentially offering an improved safety profile through restricted biodistribution. We assessed the ability of RTX-240 to expand and activate T cells and NK cells and evaluated the in vivo efficacy, pharmacodynamics and tolerability using murine models. Treatment of PBMCs with RTX-240 induced T cell and NK cell activation and proliferation. In vivo studies using mRBC-240, a mouse surrogate for RTX-240, revealed biodistribution predominantly to the red pulp of the spleen, leading to CD8 + T cell and NK cell expansion. mRBC-240 was efficacious in a B16-F10 melanoma model and led to increased NK cell infiltration into the lungs. mRBC-240 significantly inhibited CT26 tumor growth, in association with an increase in tumor-infiltrating proliferating and cytotoxic CD8 + T cells. mRBC-240 was tolerated and showed no evidence of hepatic injury at the highest feasible dose, compared with a 4-1BB agonistic antibody. RTX-240 promotes T cell and NK cell activity in preclinical models and shows efficacy and an improved safety profile. Based on these data, RTX-240 is now being evaluated in a clinical trial.