Mesenchymal stromal cells with chimaeric antigen receptors for enhanced immunosuppression

Allogeneic mesenchymal stromal cells (MSCs) are a safe treatment option for many disorders of the immune system. However, clinical trials using MSCs have shown inconsistent therapeutic efficacy, mostly owing to MSCs providing insufficient immunosuppression in target tissues. Here we show that antigen-specific immunosuppression can be enhanced by genetically modifying MSCs with chimaeric antigen receptors (CARs), as we show for E-cadherin-targeted CAR-MSCs for the treatment of graft-versus-host disease in mice. CAR-MSCs led to superior T-cell suppression and localization to E-cadherin+ colonic cells, ameliorating the animals' symptoms and survival rates. On antigen-specific stimulation, CAR-MSCs upregulated the expression of immunosuppressive genes and receptors for T-cell inhibition as well as the production of immunosuppressive cytokines while maintaining their stem cell phenotype and safety profile in the animal models. CAR-MSCs may represent a widely applicable therapeutic technology for enhancing immunosuppression.

CD19 occupancy with tafasitamab increases therapeutic index of CART19 cell therapy and diminishes severity of CRS

ABSTRACT

In the development of various strategies of anti-CD19 immunotherapy for the treatment of B-cell malignancies, it remains unclear whether CD19 monoclonal antibody therapy impairs subsequent CD19-targeted chimeric antigen receptor T-cell (CART19) therapy. We evaluated the potential interference between the CD19-targeting monoclonal antibody tafasitamab and CART19 treatment in preclinical models. Concomitant treatment with tafasitamab and CART19 showed major CD19 binding competition, which led to CART19 functional impairment. However, when CD19+ cell lines were pretreated with tafasitamab overnight and the unbound antibody was subsequently removed from the culture, CART19 function was not affected. In preclinical in vivo models, tafasitamab pretreatment demonstrated reduced incidence and severity of cytokine release syndrome and exhibited superior antitumor effects and overall survival compared with CART19 alone. This was associated with transient CD19 occupancy with tafasitamab, which in turn resulted in the inhibition of CART19 overactivation, leading to diminished CAR T apoptosis and pyroptosis of tumor cells.

Treatment strategies for relapse after CAR T-cell therapy in B cell lymphoma

Clinical trials of anti-CD19 chimeric antigen receptor T (CART19) cell therapy have shown high overall response rates in patients with relapsed/refractory B-cell malignancies. CART19 cell therapy has been approved by the US Food and Drug Administration for patients who relapsed less than 12 months after initial therapy or who are refractory to first-line therapy. However, durable remission of CART19 cell therapy is still lacking, and 30%-60% of patients will eventually relapse after CART19 infusion. In general, the prognosis of patients who relapse after CART19 cell therapy is poor, and various strategies to treat this patient population have been investigated extensively. CART19 failures can be broadly categorized by the emergence of either CD19-positive or CD19-negative lymphoma cells. If CD19 expression is preserved on the lymphoma cells, a second infusion of CART19 cells or reactivation of previously infused CART19 cells with immune checkpoint inhibitors can be considered. When patients develop CD19-negative relapse, targeting different antigens (e.g., CD20 or CD22) with CAR T cells, investigational chemotherapies, or hematopoietic stem cell transplantation are potential treatment options. However, salvage therapies for relapsed large B-cell lymphoma after CART19 cell therapy have not been fully explored and are conducted based on clinicians' case-by-case decisions. In this review, we will focus on salvage therapies reported to date and discuss the management of relapsed/refractory large B-cell lymphomas after CART19 cell therapy.

Who wins the combat, CAR or TCR?

Chimeric antigen receptor T (CAR-T) cell therapy has drawn increasing attention over the last few decades given its remarkable effectiveness and breakthroughs in treating B cell hematological malignancies. Even though CAR-T cell therapy has outstanding clinical successes, most treated patients still relapse after infusion. CARs are derived from the T cell receptor (TCR) complex and co-stimulatory molecules associated with T cell activation; however, the similarities and differences between CARs and endogenous TCRs regarding their sensitivity, signaling pathway, killing mechanisms, and performance are still not fully understood. In this review, we discuss the parallel comparisons between CARs and TCRs from various aspects and how these current findings might provide novel insights and contribute to improvement of CAR-T cell therapy efficacy.

AXL Inhibition Improves the Antitumor Activity of Chimeric Antigen Receptor T Cells

The receptor tyrosine kinase AXL is a member of the TYRO3, AXL, and proto-oncogene tyrosine-protein kinase MER family and plays pleiotropic roles in cancer progression. AXL is expressed in immunosuppressive cells, which contributes to decreased efficacy of immunotherapy. Therefore, we hypothesized that AXL inhibition could serve as a strategy to overcome resistance to chimeric antigen receptor T (CAR T)-cell therapy. To test this, we determined the impact of AXL inhibition on CD19-targeted CAR T (CART19)-cell functions. Our results demonstrate that T cells and CAR T cells express high levels of AXL. Specifically, higher levels of AXL on activated Th2 CAR T cells and M2-polarized macrophages were observed. AXL inhibition with small molecules or via genetic disruption in T cells demonstrated selective inhibition of Th2 CAR T cells, reduction of Th2 cytokines, reversal of CAR T-cell inhibition, and promotion of CAR T-cell effector functions. AXL inhibition is a novel strategy to enhance CAR T-cell functions through two independent, but complementary, mechanisms: targeting Th2 cells and reversing myeloid-induced CAR T-cell inhibition through selective targeting of M2-polarized macrophages.

Abstract 5074: Addition of MAPK inhibitors to prime and sensitize poorly differentiated thyroid cancers as a strategy to improve TSHR-CART cell therapy antitumor activity

Thyroid cancer is the most common endocrine cancer in the US, and its incidence is rising. Most thyroid cancer deaths are attributed to treatment-refractory, metastatic tumors. Thyroid stimulating hormone receptor (TSRH) expression is largely limited to the thyroid gland and is abundantly expressed on thyroid tumor cells, making TSRH a compelling target for advanced thyroid cancer diagnostics and therapeutics. Therefore, we developed a novel TSHR-targeted chimeric antigen receptor (CAR) T cell therapy to treat aggressive thyroid cancers. TSHR-CAR constructs were cloned into a lentiviral CAR construct containing 4-1BB and CD3ζ. First, we demonstrated potent TSHR-CART antigen-specific anti-tumor activity in vitro. Then, NOD-SCID-γ-/- (NSG) mice were inoculated subcutaneously with TSHR+ tumor cells and randomized by tumor volume to treatment with TSHR-CART cells or control Untransduced T cells (UTD). Treatment with TSHR-CART cells resulted in dose-dependent antitumor activity and prolonged survival. De-differentiated anaplastic thyroid cancers (ATC) downregulate TSHR. Our TSHR immunohistochemistry results corroborated these findings and displayed minimal TSHR protein expression, precluding successful TSHR-CART treatment. We therefore sought to sensitize these tumors with MAPK inhibitors, as a strategy to upregulate TSHR expression in patients with metastatic thyroid cancer. TSHR expression was upregulated in patient-derived xenograft (PDX) ATC models after one week of daily administration of the MAPK inhibitors (p=0.0024). After confirming that MAPK inhibition does not dampen TSHR-CART effector functions, we tested sequential and combination therapy of TSHR-CART with MEK and BRAF inhibition in vivo. NSG mice were engrafted with ATC BRAF-mutant PDX tumors and randomized by tumor volume to daily oral treatment with placebo or trametinib (MEK inhibitor) plus dabrafenib (BRAF inhibitor). One week later, mice received either UTD or TSHR-CART. Mice conditioned with trametinib plus dabrafenib (p=0.0018) and subsequently treated with TSHR-CART showed superior antitumor activity. However, the improved antitumor activity in this setting was transient. We therefore tested the durability of TSHR upregulation following MEK/BRAF inhibition and demonstrated that TSHR upregulation lasts less than 48-72 hours after discontinuation. Finally, we tested the combination of TSHR CART cells with MEK/BRAF inhibitors in ATC BRAF-mutant PDX tumors. Here, combining TSHR-CART cells with MEK/BRAF inhibitors result in durable control of the tumors. Collectively, our findings indicate that MEK/BRAF inhibition of de-differentiated thyroid cancers upregulated TSHR expression and enhanced TSHR-CART antitumor activity. This work represents a viable strategy to improve outcomes of patients with aggressive, metastatic thyroid cancers.

Citation Format: Claudia Manriquez Roman, Kendall J. Schick, Justyna J. Gleba, Truc N. Huynh, Elizabeth L. Siegler, James L. Miller, Aylin Alasonyalilar Demirer, Matthew L. Pawlush, Ahmet Biligili, Long K. Mai, Erin Tapper, Leo R. Sakemura, Michelle J. Cox, Carli M. Stewart, Ismail Can, Ekene J. Ogbodo, Gaofeng Cui, Georges Mer, Gloria R. Olivier, Yushi Qiu, Robert C. Smallridge, Zubair C. Abba, Han W. Tun, John A. Copland, Saad S. Kenderian. Addition of MAPK inhibitors to prime and sensitize poorly differentiated thyroid cancers as a strategy to improve TSHR-CART cell therapy antitumor activity. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5074.

Abstract 4082: Impact of immunosuppressive monocytes on CART19 cell effector functions and outcomes

CD19 directed chimeric antigen receptor T (CART19) cell therapy has resulted in remarkable outcomes in B cell malignancies and was FDA approved in multiple indications. However, durable remissions are limited to 40% of treated patients. Inhibitory myeloid cells in tumor microenvironment have been found to suppress T cell expansion and contribute to failure of CART19 cell therapy. In this study, we aimed to unravel the interactions between monocytes, CART19 cells and tumor cells to understand how monocytes-CART19 cell interactions impact CART19 cell effector functions and clinical outcomes. Two sets of experiments were conducted, 1) use of healthy CART19 cells, CD19+ tumor cells, and healthy monocytes; 2) use of brexu-cel products from ZUMA-2 clinical trial treating mantle cell lymphoma (MCL), patient-matched monocytes and circulating MCL tumor cells (n = 11; 6 durable responders, 2 relapsed after initial response and 3 non-responders).

CD28 costimulated CART19 (CART19-28ζ) cells generated in the lab from healthy donors were co-cultured with donor freshly isolated monocytes in the presence of Jeko-1 cells (a CD19+ MCL cell line). CART19 antigen specific proliferation was not inhibited by freshly isolated monocytes. When monocytes were co-cultured with CART19 and tumor cells, higher levels of eotaxin, GRO, MCP-3 and IL-7 were detected. When CART19 cells were co-cultured with the CD19+ JeKo-1 cells in the presence of ex vivo M2 polarized macrophages, CART19 antigen specific proliferation was inhibited (p=0.0045). Transwell experiments demonstrate that M2-induced CART19 inhibition is not contact dependent. Cytokine profile analysis indicated increased level of IL-1ra, IP-10 and MCP-1 and decreased level of IL-17A, sCD40L, IL-9 and MIP-1α when M2 macrophages were co-cultured with CART19 and tumor cells compared to co-cultures of tumor cells and CART19.

Then we conducted ex vivo co-cultures of brexu-cel products, autologous monocytes and circulating MCL tumor cells from MCL patients (ZUMA-2) collected prior to CART19 cell infusion. Here we observed trends of elevation of IL-13 and IL-5 and reduction of GRO, MCP-3, MIP-1β and IL-8 in non-responders, compared to responders (durable responses or relapsed patients).

Our results support that monocyte- and macrophage-dependent cytokine release could modulate CART19 effector and trafficking functions, and thus CART19 clinical outcomes. This warrants further investigation around strategies to improve durable responses to CART cell therapy.

Citation Format: Kun Yun, Reona Leo Sakemura, Michelle J. Cox, Truc Huynh, Claudia Manriquez-Roman, Olivia Sirpilla, Carli M. Stewart, James H. Girsch, Ekene J. Ogbodo, Ismail Can, Brooke Kimball, Lionel A. Kankeu Fonkoua, Mehrdad Hefazi, Michael W. Ruff, Elizabeth L. Siegler, Mike Mattie, Sao-Mai Nguyen-Mau, Simone Filosto, Saad S. Kenderian. Impact of immunosuppressive monocytes on CART19 cell effector functions and outcomes. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4082.

Abstract 1153: IL-4 depletion leads to the improvement of CART cell therapy

While chimeric antigen receptor T-cell therapy targeting CD19 (CART19) has shown remarkable success in the treatment of hematological malignancies, the durable response rates remain approximately 40% and there are limited solutions for CART cell therapy in the treatment of solid tumors. To further understand mechanisms of resistance, including CART cell exhaustion, we employed three independent approaches: 1) RNA and ATAC sequencing on unstimulated vs. exhausted healthy donor CART19 cells by utilizing an in vitro model for exhaustion, 2) RNA and ATAC sequencing on pre-infusion CART19 cell products from responders and non-responders in the Zuma-1 clinical trial that led to the FDA approval of axi-cel CART19 therapy, and 3) a genome-wide CRISPR knockout screen in healthy donor CART19 cells using our in vitro model for exhaustion.

In each of these approaches, IL-4 was identified as a regulator of CART cell dysfunction. In approach 1, ingenuity pathway analysis of genes that were both differentially accessible and expressed in exhausted compared with unstimulated CART19 cells revealed IL-4 as a top upstream regulator (p = 5E-6). In approach 2, IL-4 was one of two genes that were both upregulated and more accessible in CART19 cell products from non-responders (p < 5E-2). Finally, in approach 3, gene ontology enrichment analysis of genes that were positively selected during the genome-wide CRISPR knockout screen, revealed regulation of the IL-4 pathway as one of the top affected pathways (p = 1E-4).

Together, our data indicates a role for IL-4 in CART cell dysfunction caused by exhaustion. Investigating this mechanism further, we saw an increase in the production of IL-4 as CART cells became exhausted (p = 4E-3). Treatment of CART19 cells with human recombinant IL-4 (hrIL-4) resulted in dysfunction as evident by a decrease in antigen specific cytotoxicity (p = 4E-3) and proliferative ability (p= 6.5E-2), as well as exhaustion-specific signs of dysfunction such as an increase in the expression of the inhibitory receptor, TIM-3 (p = 3E-3) and an increase in the transcription of the exhaustion-related transcription factor EOMES (p = 1E-2).

Finally, we tested whether IL-4 neutralization enhances CART19 cell functions. Using a CD19+ JeKo-1 xenograft mouse model, we compared the combination treatment of CART19 cells and an IL-4 neutralizing monoclonal antibody (10 mg/Kg, clone # MP4-25D2) to CART19 cells and an IgG control. IL-4 neutralization in combination with CART19 cells resulted in reduced tumor burden (p = 4.6E-2), increased CART cell proliferation (p = 8E-3), and prolonged overall survival (p= 5E-2). In summary, our data indicates that 1) IL-4 induces CART cell dysfunction through a state of exhaustion and 2) IL-4 neutralization with a monoclonal antibody enhances CART cell therapy. As such, this novel combination therapy holds the potential to be translated to the clinic to improve durable responses from CART cell therapy.

Citation Format: Carli Stewart, Michelle J. Cox, Reona Sakemura, Ekene J. Ogbodo, Ismail Can, Claudia Manriquez Roman, Kun Yun, Olivia Sirpilla, James H. Girsch, Truc Huynh, Elizabeth L. Siegler, Jenny J. Kim, Mike Mattie, Nathalie Scholler, Simone Filosto, Saad S. Kenderian. IL-4 depletion leads to the improvement of CART cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1153.

CAR-T Cell Therapy: the Efficacy and Toxicity Balance

PURPOSE OF REVIEW

Chimeric antigen receptor (CAR) T cell therapy is an immunotherapy that has resulted in tremendous progress in the treatment of patients with B cell malignancies. However, the remarkable efficacy of therapy is not without significant safety concerns. Herein, we will review the unique and potentially life-threatening toxicities associated with CAR-T cell therapy and their association with treatment efficacy.

RECENT FINDINGS

Currently, CAR-T cell therapy is approved for the treatment of B cell relapsed or refractory leukemia and lymphoma, and most recently, multiple myeloma (MM). In these different diseases, it has led to excellent complete and overall response rates depending on the patient population and therapy. Despite promising efficacy, CAR-T cell therapy is associated with significant side effects; the two most notable toxicities are cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). The treatment of CAR-T-induced toxicity is supportive; however, as higher-grade adverse events occur, toxicity-directed therapy with tocilizumab, an IL-6 receptor antibody, and steroids is standard practice. Overall, a careful risk-benefit balance exists between the efficacy and toxicities of therapies. The challenge lies in the underlying pathophysiology of CAR-T-related toxicity which relies upon the activation of CAR-T cells. Some degree of toxicity is expected to achieve an effective response to therapy, and certain aspects of treatment are also associated with toxicity. As progress is made in the investigation and approval of new CARs, novel toxicity-directed therapies and toxicity-limited constructs will be the focus of attention.

Assessment of Chimeric Antigen Receptor T Cell-Associated Toxicities Using an Acute Lymphoblastic Leukemia Patient-derived Xenograft Mouse Model

Chimeric antigen receptor T (CART) cell therapy has emerged as a powerful tool for the treatment of multiple types of CD19+ malignancies, which has led to the recent FDA approval of several CD19-targeted CART (CART19) cell therapies. However, CART cell therapy is associated with a unique set of toxicities that carry their own morbidity and mortality. This includes cytokine release syndrome (CRS) and neuroinflammation (NI). The use of preclinical mouse models has been crucial in the research and development of CART technology for assessing both CART efficacy and CART toxicity. The available preclinical models to test this adoptive cellular immunotherapy include syngeneic, xenograft, transgenic, and humanized mouse models. There is no single model that seamlessly mirrors the human immune system, and each model has strengths and weaknesses. This methods paper aims to describe a patient-derived xenograft model using leukemic blasts from patients with acute lymphoblastic leukemia as a strategy to assess CART19-associated toxicities, CRS, and NI. This model has been shown to recapitulate CART19-associated toxicities as well as therapeutic efficacy as seen in the clinic.

Targeting cancer-associated fibroblasts in the bone marrow prevents resistance to CART-cell therapy in multiple myeloma

Pivotal clinical trials of B-cell maturation antigen-targeted chimeric antigen receptor T (CART)-cell therapy in patients with relapsed/refractory multiple myeloma (MM) resulted in remarkable initial responses, which led to a recent US Food and Drug Administration approval. Despite the success of this therapy, durable remissions continue to be low, and the predominant mechanism of resistance is loss of CART cells and inhibition by the tumor microenvironment (TME). MM is characterized by an immunosuppressive TME with an abundance of cancer-associated fibroblasts (CAFs). Using MM models, we studied the impact of CAFs on CART-cell efficacy and developed strategies to overcome CART-cell inhibition. We showed that CAFs inhibit CART-cell antitumor activity and promote MM progression. CAFs express molecules such as fibroblast activation protein and signaling lymphocyte activation molecule family-7, which are attractive immunotherapy targets. To overcome CAF-induced CART-cell inhibition, CART cells were generated targeting both MM cells and CAFs. This dual-targeting CART-cell strategy significantly improved the effector functions of CART cells. We show for the first time that dual targeting of both malignant plasma cells and the CAFs within the TME is a novel strategy to overcome resistance to CART-cell therapy in MM.

CAR T cell therapy and the tumor microenvironment: Current challenges and opportunities

Chimeric antigen receptor (CAR) T cell therapy has demonstrated remarkable outcomes in individuals with hematological malignancies, but its success has been hindered by barriers intrinsic to the tumor microenvironment (TME), particularly for solid tumors, where it has yet to make its mark. In this article, we provide an updated review and future perspectives on features of the TME that represent barriers to CART cell therapy efficacy, including competition for metabolic fuels, physical barriers to infiltration, and immunosuppressive factors. We then discuss novel and promising strategies to overcome these obstacles that are in preclinical development or under clinical investigation.

Challenges of CAR T-cell Therapy in CLL: Lessons Learned

Development of chimeric antigen receptor T (CART) cell therapy has led to unprecedented success against B cell leukemia and lymphoma and resulted in FDA-approved treatment protocols. Despite the initial clinical response in B cell-related malignancies, high relapse rates suggest that much work is needed to uncover mechanisms of resistance. In chronic lymphocytic leukemia (CLL), the durable activity of CAR T-cells is limited, and CART cell success is lower than in other malignancies. T cells from these patients are vulnerable to a state of dysfunction due to stresses including chronic infection, rapid cell cycle upon antigen recognition, immunosuppressive tumor microenvironment, and cancer-related treatments. T cells are also introduced to additional stresses when cultured ex vivo during the CART manufacturing process. All these factors contribute to the limited regenerative capacity of T cells, which can lead to CART treatment failure. In this short report, we will review the challenges of CAR T-cell therapy in patients with CLL and discuss potential strategies to overcome these challenges.

Development of a Clinically Relevant Reporter for Chimeric Antigen Receptor T-cell Expansion, Trafficking, and Toxicity

Although chimeric antigen receptor T (CART)-cell therapy has been successful in treating certain hematologic malignancies, wider adoption of CART-cell therapy is limited because of minimal activity in solid tumors and development of life-threatening toxicities, including cytokine release syndrome (CRS). There is a lack of a robust, clinically relevant imaging platform to monitor in vivo expansion and trafficking to tumor sites. To address this, we utilized the sodium iodide symporter (NIS) as a platform to image and track CART cells. We engineered CD19-directed and B-cell maturation antigen (BCMA)-directed CART cells to express NIS (NIS⁺CART19 and NIS⁺BCMA-CART, respectively) and tested the sensitivity of ¹⁸F-TFB-PET to detect trafficking and expansion in systemic and localized tumor models and in a CART-cell toxicity model. NIS⁺CART19 and NIS⁺BCMA-CART cells were generated through dual transduction with two vectors and demonstrated exclusive ¹²⁵I uptake in vitro. ¹⁸F-TFB-PET detected NIS⁺CART cells in vivo to a sensitivity level of 40,000 cells. ¹⁸F-TFB-PET confirmed NIS⁺BCMA-CART-cell trafficking to the tumor sites in localized and systemic tumor models. In a xenograft model for CART-cell toxicity, ¹⁸F-TFB-PET revealed significant systemic uptake, correlating with CART-cell in vivo expansion, cytokine production, and development of CRS-associated clinical symptoms. NIS provides a sensitive, clinically applicable platform for CART-cell imaging with PET scan. ¹⁸F-TFB-PET detected CART-cell trafficking to tumor sites and in vivo expansion, correlating with the development of clinical and laboratory markers of CRS. These studies demonstrate a noninvasive, clinically relevant method to assess CART-cell functions in vivo.

Leukemic extracellular vesicles induce chimeric antigen receptor T cell dysfunction in chronic lymphocytic leukemia

Chimeric antigen receptor (CAR) T cell therapy has yielded unprecedented outcomes in some patients with hematological malignancies; however, inhibition by the tumor microenvironment has prevented the broader success of CART cell therapy. We used chronic lymphocytic leukemia (CLL) as a model to investigate the interactions between the tumor microenvironment and CART cells. CLL is characterized by an immunosuppressive microenvironment, an abundance of systemic extracellular vesicles (EVs), and a relatively lower durable response rate to CART cell therapy. In this study, we characterized plasma EVs from untreated CLL patients and identified their leukemic cell origin. CLL-derived EVs were able to induce a state of CART cell dysfunction characterized by phenotypical, functional, and transcriptional changes of exhaustion. We demonstrate that, specifically, PD-L1+ CLL-derived EVs induce CART cell exhaustion. In conclusion, we identify an important mechanism of CART cell exhaustion induced by EVs from CLL patients.

Resistance to CART cell therapy: lessons learned from the treatment of hematological malignancies

Chimeric antigen receptor T (CART) cell immunotherapy has yielded significant clinical success in treating certain hematological malignancies. However, despite high initial response rates, most patients eventually relapse. Resistance to CART cell therapy can stem from tumor cell mutations, T cell defects, and tumor microenvironment (TME) immunosuppression. Tumor cells can downregulate target antigen expression to evade CART cell detection or mutate death receptor pathways to resist CART cell cytotoxicity. Patient T cells can be intrinsically defective, and CART cells often undergo exhaustion. The TME is abundant with immunosuppressive cells and factors which contribute to suboptimal CART cell activity. Collectively, issues originating in tumor cells, T cells, and the TME present significant hurdles to long-term remission after CART cell therapy. Various strategies to combat CART cell resistance have shown promise in preclinical studies and early clinical trials and are crucial to achieving durable responses.

In vivo CART cell imaging: Paving the way for success in CART cell therapy

Chimeric antigen receptor T (CART) cells are a promising immunotherapy that has induced dramatic anti-tumor responses in certain B cell malignancies. However, CART cell expansion and trafficking are often insufficient to yield long-term remissions, and serious toxicities can arise after CART cell administration. Visualizing CART cell expansion and trafficking in patients can detect an inadequate CART cell response or serve as an early warning for toxicity development, allowing CART cell treatment to be tailored accordingly to maximize therapeutic benefits. To this end, various imaging platforms are being developed to track CART cells in vivo, including nonspecific strategies to image activated T cells and reporter systems to specifically detect engineered T cells. Many of these platforms are clinically applicable and hold promise to provide valuable information and guide improved CART cell treatment.

CART Cell Toxicities: New Insight into Mechanisms and Management

T cells genetically engineered with chimeric antigen receptors (CART) have become a potent class of cancer immunotherapeutics. Numerous clinical trials of CART cells have revealed remarkable remission rates in patients with relapsed or refractory hematologic malignancies. Despite recent clinical success, CART cell therapy has also led to significant morbidity and occasional mortality from associated toxicities. Cytokine release syndrome (CRS) and Immune effector cell-associated neurotoxicity syndrome (ICANS) present barriers to the extensive use of CART cell therapy in the clinic. CRS can lead to fever, hypoxia, hypotension, coagulopathies, and multiorgan failure, and ICANS can result in cognitive dysfunction, seizures, and cerebral edema. The mechanisms of CRS and ICANS are becoming clearer, but many aspects remain unknown. Disease type and burden, peak serum CART cell levels, CART cell dose, CAR structure, elevated pro-inflammatory cytokines, and activated myeloid and endothelial cells all contribute to CART cell toxicity. Current guidelines for the management of toxicities associated with CART cell therapy vary between clinics, but are typically comprised of supportive care and treatment with corticosteroids or tocilizumab, depending on the severity of the symptoms. Acquiring a deeper understanding of CART cell toxicities and developing new management and prevention strategies are ongoing. In this review, we present findings in the mechanisms and management of CART cell toxicities.

A Concise Review of Neurologic Complications Associated with Chimeric Antigen Receptor T-cell Immunotherapy

Chimeric antigen receptor-engineered T (CAR-T) cell immunotherapy has been successful in treating many types of hematological malignancies. CAR-T therapy, however, has been associated with toxicities, including cytokine release syndrome (CRS) as well as immune effector cell-associated neurotoxicity syndrome (ICANS). ICANS presentation is variable, largely reversible, and manifests with encephalopathy and focal neurologic deficits. Treatment strategies largely are supportive. ICANS pathophysiology likely is related to that of CRS. Preclinical studies and clinical experience have shed light on the driving forces of ICANS and have yielded new strategies to mitigate ICANS occurrence.

Neurotoxicity and Cytokine Release Syndrome After Chimeric Antigen Receptor T Cell Therapy: Insights Into Mechanisms and Novel Therapies

Chimeric antigen receptor T (CART) cell immunotherapy has been remarkably successful in treating certain relapsed/refractory hematological cancers. However, CART cell therapy is also associated with toxicities which present an obstacle to its wider adoption as a mainstay for cancer treatment. The primary toxicities following CART cell administration are cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). New insights into the mechanisms of these toxicities have spurred novel treatment options. In this review, we summarize the available literature on the clinical manifestations, mechanisms, and treatments of CART-associated CRS and ICANS.

ERK Activation in CAR T Cells Is Amplified by CD28-Mediated Increase in CD3ζ Phosphorylation

Chimeric antigen receptors (CARs) are engineered receptors that mediate T cell activation. CARs are comprised of activating and co-stimulatory intracellular signaling domains derived from endogenous T cells that initiate signaling required for T cell activation, including ERK activation through the MAPK pathway. Understanding the mechanisms by which co-stimulatory domains influence signaling can help guide the design of next-generation CARs. Therefore, we constructed an experimentally validated computational model of anti-CD19 CARs in T cells bearing the CD3ζ domain alone or in combination with CD28. We performed a systematic analysis to explore the different mechanisms of CD28 co-stimulation on the ERK response time. Comparing these model simulations with experimental data indicates that CD28 primarily influences ERK activation by enhancing the phosphorylation kinetics of CD3ζ. Overall, we present a mechanistic mathematical modeling framework that can be used to gain insights into the mechanism of CAR T cell activation and produce new testable hypotheses.

Abstract A59: Expression of membrane-bound IL-15/IL-15Rα complex in chimeric antigen receptor-engineered natural killer cells for enhanced efficacy against solid tumors

The natural killer cell line NK92 has shown exciting potential as an anticancer immunotherapeutic tool in both preclinical models and in clinical trials. Preclinical studies have demonstrated improved antitumor responses after modifying NK92 cells with chimeric antigen receptors (CARs), which redirect immune cell activity to target cancer cells. CARs typically contain an antibody-derived extracellular domain, which binds to the desired tumor-associated antigen (TAA) and triggers an intracellular signaling cascade to activate the immune cell against the target cell. While CAR-based therapies have had remarkable success in treating hematological cancers, treatment of solid tumors has encountered many obstacles, including a lack of persistence and immunosuppression within the tumor microenvironment. Researchers have tried to circumvent these issues through the systemic delivery of cytokines such as IL-2 and IL-15. However, the delivery of supraphysiological cytokine concentrations is inefficient and has led to toxicities and unwanted side effects in the clinic. More recently, immune cells have been modified to ectopically express cytokines such as IL-15 to provide autocrine stimulation. IL-15 has been shown to activate and promote the proliferation of immune cells such as T and NK cells upon binding to its receptor, IL-15Rα. Recombinant IL-15 bound to IL-15Rα has been tested in clinical trials to boost antitumor immunity, as it imitates the physiological transpresentation of endogenous IL-15.

We have transduced NK92 cells with either a CAR targeted against the human TAA mesothelin (αmeso.NK) or a bicistronic vector containing the αmeso CAR and a membrane-bound human IL-15/IL-15Rα complex (αmeso.mbIL15.NK). Both retroviral vectors demonstrated efficient transduction of NK92 cells, with 55% and 40% transduction efficiency, respectively. CAR+ populations were further selected via fluorescence activated cell sorting. The inclusion of the mbIL15 complex allowed the αmeso.mbIL15.NK cells to continue to proliferate in vitro in the absence of exogenous IL-2 and further enriched CAR expression when tested in an unsorted population. In contrast, αmeso.NK cells without the mbIL15 complex were unable to proliferate without exposure to IL-2 in culture, resulting in cell death and loss of CAR expression within five days. We will compare αmeso.NK and αmeso.mbIL15.NK cells to determine if the mbIL15 complex enhances cytokine secretion and cytotoxicity in the presence of mesothelin-expressing cancer cells in vitro. We further hypothesize that αmeso.mbIL15.NK cells will demonstrate superior proliferation and persistence in a mouse model without additional cytokine supplementation when compared to αmeso.NK cells. NK92 cells represent a viable allogenic, off-the-shelf anticancer immunotherapy, and CAR-engineered NK92 cells have shown promise in preclinical solid tumor models. The addition of membrane-bound IL-15/IL-15Rα complex may further enhance cytotoxic effects as well as persistence and resistance to immune exhaustion within the tumor microenvironment.

Citation Format: Elizabeth L. Siegler, Pin Wang. Expression of membrane-bound IL-15/IL-15Rα complex in chimeric antigen receptor-engineered natural killer cells for enhanced efficacy against solid tumors [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A59.

Combination Cancer Therapy Using Chimeric Antigen Receptor-Engineered Natural Killer Cells as Drug Carriers

The therapeutic limitations of conventional chemotherapeutic drugs include chemo-resistance, tumor recurrence, and metastasis. Numerous nanoparticle-based active targeting approaches have emerged to enhance the intracellular concentration of drugs in tumor cells; however, efficient delivery of these systems to the tumor site while sparing healthy tissue remains elusive. Recently, much attention has been given to human immune-cell-directed nanoparticle drug delivery, because immune cells can traffic to the tumor and inflammatory sites. Natural killer cells are a subset of cytotoxic lymphocytes that play critical roles in cancer immunosurveillance. Engineering of the human natural killer cell line, NK92, to express chimeric antigen receptors to redirect their antitumor specificity has shown significant promise. We demonstrate that the efficacy of chemotherapy can be enhanced in vitro and in vivo while reducing off-target toxicity by using chimeric antigen receptor-engineered NK92 cells as carriers to direct drug-loaded nanoparticles to the target site.

The medical interview: differences between adult and geriatric outpatients

BACKGROUND

There is a perception that primary care physicians spend less time with older patients and little is known about physician and older patient satisfaction during clinical encounters.

OBJECTIVE

To determine how primary care interviews of geriatric patients differ from those of other adults.

DESIGN

Descriptive, analytic study.

SETTING

Ten primary care sites in the United States and one in Canada, including public, voluntary, and private clinics and practices.

PARTICIPANTS

Of the 544 patients, 45.6% were 65 and older and 17.8% were 75 or older. There were 127 participating physicians.

MEASUREMENTS

Encounters were audiotaped and analyzed. Patients and physicians also completed exit questionnaires.

RESULTS

Interview length increased significantly with age for men but not for women. Physician satisfaction did not change as patient age increased. Patient satisfaction, on the other hand decreased with age among women but not for men. Although physicians' and younger patients' perceptions of health were moderately associated, there was no association for men ages 75 and over.

CONCLUSIONS

There is no evidence that physicians spend less time or are more uncomfortable with older patients. Both physician and male patient satisfaction remain stable with increasing patient age, despite greater disparity in patient and physician perceptions of health. Older female patients are less satisfied with physician visits than their younger counterparts, in the absence of changes in interview length or disparities between older female patients and their physicians in health perception.

Physician-older patient communication at the end of life

Communication with dying patients and their families requires special skills to assist them in this extremely stressful period. This article begins with a case that illustrates many of the challenges of communicating with the dying. It then reviews the literature about communication with older patients at the end of life, focusing on physician-patient discussions, decision-making, advance directives, and cultural factors. The article concludes with a practical discussion of problems that physicians may encounter when working with older patients at the end of life and their families and recommendations to improve communication.

How to get the most benefit from a changing home health care system

By 1998, a Medicare prospective payment system for home care is expected to be in place. Physicians must become more involved in home care, because they will be held accountable for the patients they refer and the services they order.

Effects of a restraint reduction intervention and OBRA '87 regulations on psychoactive drug use in nursing homes

OBJECTIVES

To describe the changes in psychoactive drug use in nursing homes after implementation of physical restraint reduction interventions and mandates of the Omnibus Budget Reconciliation Act of 1987 (OBRA '87).

METHODS

A secondary analysis was conducted using data from a controlled clinical trial that took place in three nursing homes: a control home, one that received an educational intervention, and one that received an educational/consultation intervention. All three homes were influenced by the OBRA mandates. Complete pre- and 6 months' post-intervention data on use of psychoactive drugs and physical restraints were available for 446 resident subjects. Changes were first analyzed with the resident subjects as the unit of analysis and then using the nursing home ward (n = 16) as the unit of analysis.

RESULTS

While physical restraint use declined in the home that received the educational/consultation intervention, neither neuroleptic nor benzodiazepine use increased in any of the homes after the interventions. The percentage of residents taking neuroleptics declined in the control home (18.6% to 11.3%, P = .014). Benzodiazepine use, which was more prevalent than described previously in the literature, declined in all three homes (P < .001). Of those residents whose physical restraints were discontinued, only 2% were started on neuroleptics. When the effect of OBRA mandates on appropriateness of neuroleptic use was examined, the percentage of residents on neuroleptics who lacked an OBRA-approved indication declined from 21.3% to 14.6% in the total sample, and from 39.9% to 8% in the control home.

CONCLUSIONS

Interventions to reduce physical restraint did not lead to an increase in psychoactive drug use; further, reduction in both can occur simultaneously. OBRA mandates regarding psychoactive drug use were not uniformly effective, but appear, at minimum, to have increased awareness of the indications for neuroleptics.

Antimicrobial resistance patterns in long term geriatric care. Implications for drug therapy

There is a high prevalence of bacterial infections in long term care facilities (4.4 to 16.2%). This, together with the fact that antimicrobial resistance is a big concern in current medical practice, makes infection control so important in nursing home care. This article covers the mechanisms of antibacterial resistance and focuses on 4 major antibacterial-resistant bacteria. Vancomycin is the treatment of choice for methicillin-resistant Staphylococcus aureus (MRSA). Colonisation with MRSA is not uncommon in nursing homes and eradication is probably not necessary. Any clinically important enterococcal infection should be tested for high-level resistance. An infectious disease consultation should be sought for vancomycin-resistant enterococcal infections. Gram-negative bacilli have developed multi-resistance. Susceptibility testing can identify the most appropriate therapy. Multiresistance should also be considered when treating Streptococcus pneumoniae. Overall, handwashing is highly recommended. Barrier precautions, minimising hospitalisations and avoiding unnecessary personnel rotation can reduce the chance of resistance spread.

The CARE Program: a nurse-managed collaborative outpatient program to improve function of frail older people. Collaborative Assessment and Rehabilitation for Elders

BACKGROUND AND OBJECTIVES

Frail older adults are especially vulnerable in a health system that is fragmented and fails to focus on preservation or restoration of function. The School of Nursing at the University of Pennsylvania, together with the School of Medicine and the Hospital of the University of Pennsylvania, established the Collaborative Assessment and Rehabilitation for Elders (CARE) Program to meet the needs of this population. We used the British Day Hospital as a model because it provides a comprehensive approach to care and a bridge between acute, home-based, and institutional long-term care. We have designed our program to provide innovative, interdisciplinary care as well as to be reimbursable under current and future payment structures. This nurse-managed, collaborative practice seeks to maximize independent functioning, promote health, and enhance quality of life for chronically ill, frail older adults living in the community whose needs are left unmet by existing services. The program was certified as a Comprehensive Outpatient Rehabilitation Facility (CORF) in December 1993 to maximize reimbursement of services through Medicare and other third party payers. With a Gerontological Nurse Practitioner as care manager, clients receive an intensive, individualized, time-limited program of nursing, rehabilitation, mental health, social, and medical services in one setting several days each week. Additional geriatric services, such as primary care, are available in the same location when needed.

SETTING

The program is housed in renovated space devoted to the care of older people. The academic and clinical offices of the University of Pennsylvania's nursing and medical gerontologic and geriatric faculty are in the same building.

PARTICIPANTS

We have targeted those persons older than age 65 who have complex health problems and are living at home. Individuals must need multiple services, including at least one rehabilitation therapy, and they must be unsuitable-for inpatient rehabilitation. DESCRIPTION OF THE POPULATION: In its first 8 months of operation, the program received 97 referrals and admitted 53 clients. Clients were, on average, 78 years of age. Over three-fourths (77%) were women and 58% were black. The average stay in the program was 6 weeks. FIM scores, which improved a mean of 2.4 points, were found to lack sensitivity to the functional improvements achieved by clients.

CONCLUSION

Under existing Medicare and third party reimbursement policies, it is feasible to establish a nurse-managed comprehensive outpatient rehabilitation program designed to meet the needs of frail older persons. Preliminary data support the beneficial effects of the program as well as the economic feasibility of this approach.

Risk factors for the development of hyponatremia in psychiatric inpatients

BACKGROUND

When inpatients who are on psychiatry services develop hyponatremia, medical consultation is usually required for evaluation and management, thus halting or delaying psychiatric treatment. Risk factors for the development of hyponatremia in this population have not been studied.

METHODS

A case-control study of psychiatric inpatients in a tertiary care facility was performed. Sixty-four patients who had a serum sodium level of less than 130 mmol/L were identified; three control subjects were chosen from the inpatient psychiatry service for each case. Risk factors investigated included medications, psychiatric diagnoses, basic demographic variables, and medical comorbidities.

RESULTS

Univariate and logistic regression analyses revealed that, in addition to diuretic use (adjusted odds ratio, 8.2; 95% confidence intervals, 2.2 to 30.8), use of fluoxetine (adjusted odds ratio, 21.4; 95% confidence interval, 5.3 to 86.9), tricyclic antidepressants (adjusted odds ratio, 4.9; 95% confidence interval, 1.6 to 15.2), and calcium antagonists (adjusted odds ratio, 4.0; 95% confidence interval, 1.1 to 14.2) were all associated with the development of hyponatremia. Important comorbidities included elevated creatinine levels, chronic obstructive pulmonary disease, hypertension, systolic blood pressure, and diabetes. Although age was significantly associated with hyponatremia in univariate analyses, it was not significant in multivariate analyses.

CONCLUSIONS

Among psychiatric patients, hyponatremia is often associated with factors other than psychogenic polydipsia, including medications and medical comorbidities. Although elderly psychiatric inpatients seem to develop hyponatremia more often than younger patients, once drugs and comorbidities are taken into account, age does not appear to be a significant risk factor for hyponatremia in this population.

Development of complications during rehabilitation

BACKGROUND AND METHODS

Although studies have demonstrated that medical rehabilitation patients have many complications that warrant attention, none has attempted to categorize complications by severity. This retrospective cohort study examined the incidence, types, and severity of problems that interrupt rehabilitation and the major risk factors for these events.

RESULTS

Of 1075 patients, 359 (33.4%) had acute medical complications on rehabilitation considered severe enough to interrupt treatment. Of the 359 patients, 158 (44%) required an unexpected transfer off rehabilitation. The most common reasons for unexpected transfer were surgical causes (22.8%), followed by infection or fever (17.1%) and by thromboembolic events (16.5%). Logistic regression revealed that major risk factors for complications requiring transfer were a primary diagnosis of deconditioning or nontraumatic spinal cord injury (adjusted odds ratio, 2.7; confidence interval, 1.8 to 4.2), severity of initial disability (adjusted odds ratio, 1.2; confidence interval, 1.1 to 1.3 for every 10-point drop in a Modified Barthel Index), and number of comorbid conditions (adjusted odds ratio, 1.1; confidence interval, 1.0 to 1.2). Risk factors for any complication were similar, but there was an interaction between comorbidity and the degree of functional impairment; in patients who were severely functionally impaired, the number of comorbidities was not as strongly associated with the risk of complications as it was in patients who were less functionally impaired.

CONCLUSION

There is a complex relationship among the type of underlying medical impairment, severity of functional limitation, comorbidity, and unanticipated medical or surgical complications that interrupt rehabilitation. The interruptions vary both in type and in severity.

Methicillin-resistant Staphylococcus aureus colonization in a new nursing home

Methicillin-resistant Staphylococcus aureus (MRSA) has been detected in nursing homes and long-term care facilities. Studies disagree about the risk of infection with MRSA in colonized patients. MRSA colonization and infection were tracked for one year in all admissions to a 60-bed ward at the Philadelphia VA Nursing Home Care Unit (NHCU) from the time of its opening in June, 1990. Patients and staff were blinded to culture results, and the NHCU followed universal precautions for all patients. Of the first 72 patients, 7 were found to be colonized with MRSA; only one of them was known to have had MRSA prior to NHCU transfer. Three patients died (2 had negative cultures prior to death), and 1 was discharged home. Three patients spontaneously cleared MRSA colonization and lived to the end of the study. Three patients appeared to be colonized by MRSA after admission; subsequent cultures were negative. No patients were infected by MRSA in the NHCU. At the close of the study, one year after the nursing home opened, no patient in the nursing home had a culture positive for MRSA. In conclusion, colonization with MRSA at the time of admission to the nursing home is not uncommon, but patients can spontaneously clear it. Besides, nursing homes that pre-screen only those patients with classic risk factors may be admitting many MRSA-colonized patients. Nonetheless, universal precautions appear to be effective in limiting transmission of MRSA in the nursing home; in this study, MRSA acquisition was sporadic and brief.

Collaboration in the preparation of the generalist physician

Collaborative efforts among health care professionals and institutions at all levels will be essential to the increased production of generalist physicians. There have been many successful collaborations in education and patient care among certifying boards, faculty, physicians in practice, specialists, generalists, and non-physician health professionals, as well as among the three generalist specialties. Recommended strategies to encourage collaboration in the preparation of generalist physicians include: creation of an institutional collaborative curriculum committee; design of a longitudinal curriculum on collaboration for physicians-in-training and other health professionals; implementation of collaborative patient care in ambulatory care teaching clinics; development of integrated systems of care that link inpatient, outpatient, and community-based health services; and education of physicians-in-training in these and other collaborative and co-practice models of patient care.

Silent ischemia in rehabilitation patients: limited clinical utility of electrocardiographic monitoring

In a prospective blinded trial, 24-hour continuous electrocardiographic monitoring for silent ischemia was used to try to identify rehabilitation patients at risk for cardiac complications. Five of 42 patients had episodes of silent ischemia, none of which occurred during physical therapy sessions. One of these patients had syncope while wearing the Holter; none of the other four patients had significant cardiac complications during their rehabilitation, and all were discharged home. None of the patients without ischemia on the monitor had complications, but two patients of 14 whose ECGs precluded monitoring for ischemia had complications. In addition, six patients had episodes of nonsustained asymptomatic ventricular tachycardia, 12 had episodes of supraventricular tachycardia, and four had significant ventricular ectopy, all without clinical significance. Despite the apparent high sensitivity and specificity of the technique, the positive predictive value of monitoring eligible patients for silent ischemia was 20%. We conclude that ambulatory electrocardiographic monitoring for silent ischemia or ectopy has limited clinical utility in the rehabilitation population.

Management of stage III pressure ulcers in moderately demented nursing home residents

PURPOSE

To determine whether the myocutaneous flap procedure, the preferred treatment for young patients with stage III pressure ulcers, is appropriate for moderately demented nursing home residents.

SUBJECTS AND METHODS

A model of the treatment decision was created using the decision-tree format. The probabilities of treatment outcomes in the decision tree were derived from the literature. Utilities for treatment outcomes were obtained from five internists, five geriatricians, six nurse practitioners, five plastic surgeons, and six lay people.

RESULTS

A majority in each group of respondents favored surgery, according to the decision analysis. Sensitivity analysis showed that surgery was preferred unless its success rate was less than 30%, or the rate of healing with conservative measures was at least 40%, which are unlikely values. Economic analysis demonstrated that surgery was $17,000 more expensive than conservative therapy.

CONCLUSION

The myocutaneous flap procedure is preferred by the majority of relevant decision makers when cost is not a consideration. The relative underutilization of surgery in practice has many possible explanations. The most likely are the failure of providers to appreciate the morbidity of pressure ulcers and the reluctance of practitioners to perform expensive procedures on demented patients.