Sneha Ramakrishna

All Publications

• Use of cardiac radiation therapy as bridging therapy to CAR-T for relapsed pediatric B-cell acute lymphoblastic leukemia. Pediatric blood & cancer Marquez, C. P., Montiel-Esparza, R., Hui, C., Schultz, L. M., Davis, K. L., Hoppe, R. T., Donaldson, S. S., Ramakrishna, S., Hiniker, S. M. 2020: e28870

  Abstract

  The use of radiotherapy as bridging therapy to chimeric antigen receptor T-cell therapy (CAR-T) in pre-B acute lymphoblastic leukemia (B-ALL) has been minimally explored. Here, we present a boy with B-ALL who relapsed after allogeneic bone marrow transplant with disseminated disease, including significant symptomatic cardiovascular and gastrointestinal (GI) involvement. The cardiac and GI leukemic infiltrates were successfully treated with bridging radiation therapy (BRT) prior to CAR-T infusion. Using this approach, he successfully tolerated CAR-T with no evidence of disease or sequelae on 3-month follow-up. This is the first reported case of safe and effective delivery of cardiac BRT in B-ALL.

  View details for DOI 10.1002/pbc.28870

  View details for PubMedID 33355997

• Using single-cell analysis to predict CAR T cell outcomes. Nature medicine Ramakrishna, S., Shah, N. N. 2020

  View details for DOI 10.1038/s41591-020-01157-w

  View details for PubMedID 33230341

• Identification of dual positive CD19+/CD3+ T cells in a leukapheresis product undergoing CAR transduction: a case report. Journal for immunotherapy of cancer Schultz, L., Patel, S., Davis, K. L., Ramakrishna, S., Sahaf, B., Bhatia, N., Baggott, C., Erickson, C., Majzner, R. G., Oak, J., Bertaina, A., Mackall, C., Feldman, S. 2020; 8 (2)

  Abstract

  BACKGROUND: Chimeric antigen receptor (CAR) therapy and hematopoietic stem cell transplantation (HSCT) are therapeutics for relapsed acute lymphocytic leukemia (ALL) that are increasingly being used in tandem. We identified a non-physiologic CD19+/CD3+ T-cell population in the leukapheresis product of a patient undergoing CAR T-cell manufacturing who previously received a haploidentical HSCT, followed by infusion of a genetically engineered T-cell addback product. We confirm and report the origin of these CD19+/CD3+ T cells that have not previously been described in context of CAR T-cell manufacturing. We additionally interrogate the fate of these CD19-expressing cells as they undergo transduction to express CD19-specific CARs.MAIN BODY: We describe the case of a preteen male with multiply relapsed B-ALL who was treated with sequential cellular therapies. He received an alphabeta T-cell depleted haploidentical HSCT followed by addback of donor-derived T cells genetically modified with a suicide gene for iCaspase9 and truncated CD19 for cell tracking (RivoCel). He relapsed 6months following HSCT and underwent leukapheresis and CAR T-cell manufacturing. During manufacturing, we identified an aberrant T-cell population dually expressing CD19 and CD3. We hypothesized that these cells were RivoCel cells and confirmed using flow cytometry and PCR that the identified cells were in fact RivoCel cells and were eliminated with iCaspase9 activation. We additionally tracked these cells through CD19-specific CAR transduction and notably did not detect T cells dually positive for CD19 and CD19-directed CARs. The most likely rationale for this is in vitro fratricide of the CD19+ 'artificial' T-cell population by the CD19-specific CAR+ T cells in culture.CONCLUSIONS: We report the identification of CD19+/CD3+ cells in an apheresis product undergoing CAR transduction derived from a patient previously treated with a haploidentical transplant followed by RivoCel addback. We aim to bring attention to this cell phenotype that may be recognized with greater frequency as CAR therapy and engineered alphabetahaplo-HSCT are increasingly coupled. We additionally suggest consideration towards using alternative markers to CD19 as a synthetic identifier for post-transplant addback products, as CD19-expression on effector T cells may complicate subsequent treatment using CD19-directed therapy.

  View details for DOI 10.1136/jitc-2020-001073

  View details for PubMedID 32929049

• Delayed cancer diagnoses and high mortality in children during the COVID-19 pandemic. Pediatric blood & cancer Ding, Y., Ramakrishna, S., Long, A. H., Phillips, C. A., Montiel-Esparza, R., Diorio, C. J., Bailey, L. C., Maude, S. L., Aplenc, R., Batra, V., Reilly, A. F., Rheingold, S. R., Lacayo, N. J., Sakamoto, K. M., Hunger, S. P. 2020: e28427

  View details for DOI 10.1002/pbc.28427

  View details for PubMedID 32588960

• Prospects and Challenges for Use of CAR T Cell Therapies in Solid Tumors. Expert opinion on biological therapy Ramakrishna, S., Barsan, V., Mackall, C. 2020

  Abstract

  Introduction: Chimeric antigen receptor (CAR) T cell therapy has provided patients with relapsed/refractory B cell malignancies with a new therapeutic option, but this class of therapeutics has not demonstrated consistent therapeutic benefit in solid tumors.Areas Covered: Here we review the literature to identify numerous factors that contribute to this discrepancy, using pediatric cancers as a platform to understand these limitations. We discuss an inability to target highly and homogenously expressed lineage-associated antigens due to risks of on-target, off-tumor toxicity, T cell dysfunction related to T cell exhaustion and the suppressive tumor microenvironment (TME), and inefficient CAR T cell trafficking into solid tumors. As our understanding of the biology of CAR T cells improves and innovations in engineering CAR platforms emerge, next generation CAR T cell therapeutics designed to overcome these challenges will enter the clinic for testing.Expert Opinion: New approaches to address the challenges that have limited the efficacy of CAR T cell therapeutics in solid tumors are emerging. These include next-generation CAR T cell engineering to overcome antigen heterogeneity, to mitigate T cell exhaustion and to prevent suppression by the TME, and novel approaches for regional delivery to overcome limitations in tumor T cell trafficking.

  View details for DOI 10.1080/14712598.2020.1738378

  View details for PubMedID 32125191

• Immunotherapy for the Treatment of Acute Lymphoblastic Leukemia. Current oncology reports Barsan, V., Ramakrishna, S., Davis, K. L. 2020; 22 (2): 11

  Abstract

  PURPOSE OF REVIEW: Immunotherapy for the treatment of acute lymphoblastic leukemia (ALL) broadens therapeutic options beyond chemotherapy and targeted therapy. Here, we review the use of monoclonal antibody-based drugs and cellular therapies to treat ALL. We discuss the challenges facing the field regarding the optimal timing and sequencing of these therapies in relation to other treatment options as well as considerations of cost effectiveness.RECENT FINDINGS: By early identification of patients at risk for leukemic relapse, monoclonal antibody and cellular immunotherapies can be brought to the forefront of treatment options. Novel CAR design and manufacturing approaches may enhance durable patient response. Multiple clinical trials are now underway to evaluate the sequence and timing of monoclonal antibody, cellular therapy, and/or stem cell transplantation. The biologic and clinical contexts in which immunotherapies have advanced the treatment of ALL confer optimism that more patients will achieve durable remissions. Immunotherapy treatments in ALL will expand through rationally targeted approaches alongside advances in CAR T cell therapy design and clinical experience.

  View details for DOI 10.1007/s11912-020-0875-2

  View details for PubMedID 31997022

• Supercharging your CAR. Blood Ramakrishna, S., Davis, K. L. 2020; 135 (9): 593–94

  View details for DOI 10.1182/blood.2019004469

  View details for PubMedID 32106308

• Modulation of Target Antigen Density Improves CAR T Cell Functionality and Persistence. Clinical cancer research : an official journal of the American Association for Cancer Research Ramakrishna, S., Highfill, S. L., Walsh, Z., Nguyen, S. M., Lei, H., Shern, J. F., Qin, H., Kraft, I. L., Stetler-Stevenson, M., Yuan, C. M., Hwang, J. D., Feng, Y., Zhu, Z., Dimitrov, D., Shah, N. N., Fry, T. 2019

  Abstract

  Chimeric antigen receptor T cell (CART) therapy targeting CD22 induces remission in 70% of patients with relapsed/refractory acute lymphoblastic leukemia (ALL). However, the majority of post-CD22 CART remissions are short and associated with reduction in CD22 expression. We evaluate the implications of low antigen density on the activity of CD22 CART and propose mechanisms to overcome antigen escape.Using ALL cell lines with variable CD22 expression, we evaluate the cytokine profile, cytotoxicity, and in vivo CART functionality in the setting of low CD22 expression. We develop a high-affinity CD22 CAR as an approach to improve CAR sensitivity. We also assess Bryostatin1, a therapeutically relevant agent, to upregulate CD22 and improve CAR functionality.We demonstrate that low CD22 expression negatively impacts in vitro and in vivo CD22 CART functionality and impairs in vivo CART persistence. Moreover, low antigen expression on leukemic cells increases naïve phenotype of persisting CART. Increasing CAR affinity does not improve response to low-antigen leukemia. Bryostatin1 upregulates CD22 on leukemia and lymphoma cell lines for 1 week following single-dose exposure, improves CART functionality and in vivo persistence. While Bryostatin1 attenuates IFN-gamma production by CART, overall in vitro and in vivo CART cytotoxicity is not adversely affected. Finally, administration of Bryostain1 with CD22 CAR results in longer duration of in vivo response.We demonstrate that target antigen modulation is a promising strategy to improve CD22 CAR efficacy and remission durability in patients with leukemia and lymphoma.

  View details for DOI 10.1158/1078-0432.CCR-18-3784

  View details for PubMedID 31110075

• Preclinical Development of Bivalent Chimeric Antigen Receptors Targeting Both CD19 and CD22 MOLECULAR THERAPY-ONCOLYTICS Qin, H., Ramakrishna, S., Nguyen, S., Fountaine, T. J., Ponduri, A., Stetler-Stevenson, M., Yuan, C. M., Haso, W., Shern, J. F., Shah, N. N., Fry, T. J. 2018; 11: 127–37

  Abstract

  Despite high remission rates following CAR-T cell therapy in B-ALL, relapse due to loss of the targeted antigen is increasingly recognized as a mechanism of immune escape. We hypothesized that simultaneous targeting of CD19 and CD22 may reduce the likelihood of antigen loss, thus improving sustained remission rates. A systematic approach to the generation of CAR constructs incorporating two target-binding domains led to several novel CD19/CD22 bivalent CAR constructs. Importantly, we demonstrate the challenges associated with the construction of a bivalent CAR format that preserves bifunctionality against both CD19 and CD22. Using the most active bivalent CAR constructs, we found similar transduction efficiency compared to that of either CD19 or CD22 single CARs alone. When expressed on human T cells, the optimized CD19/CD22 CAR construct induced comparable interferon γ and interleukin-2 in vitro compared to single CARs against dual-antigen-expressing as well as single-antigen-expressing cell lines. Finally, the T cells expressing CD19/CD22 CAR eradicated ALL cell line xenografts and patient-derived xenografts (PDX), including a PDX generated from a patient with CD19- relapse following CD19-directed CAR therapy. The CD19/CD22 bivalent CAR provides an opportunity to test whether simultaneous targeting may reduce risk of antigen loss.

  View details for DOI 10.1016/j.omto.2018.10.006

  View details for Web of Science ID 000454075900012

  View details for PubMedID 30581986

  View details for PubMedCentralID PMC6300726

• CD22-targeted CAR T cells induce remission in B-ALL that is naive or resistant to CD19-targeted CAR immunotherapy. Nature medicine Fry, T. J., Shah, N. N., Orentas, R. J., Stetler-Stevenson, M., Yuan, C. M., Ramakrishna, S., Wolters, P., Martin, S., Delbrook, C., Yates, B., Shalabi, H., Fountaine, T. J., Shern, J. F., Majzner, R. G., Stroncek, D. F., Sabatino, M., Feng, Y., Dimitrov, D. S., Zhang, L., Nguyen, S., Qin, H., Dropulic, B., Lee, D. W., Mackall, C. L. 2017

  Abstract

  Chimeric antigen receptor (CAR) T cells targeting CD19 mediate potent effects in relapsed and/or refractory pre-B cell acute lymphoblastic leukemia (B-ALL), but antigen loss is a frequent cause of resistance to CD19-targeted immunotherapy. CD22 is also expressed in most cases of B-ALL and is usually retained following CD19 loss. We report results from a phase 1 trial testing a new CD22-targeted CAR (CD22-CAR) in 21 children and adults, including 17 who were previously treated with CD19-directed immunotherapy. Dose-dependent antileukemic activity was observed, with complete remission obtained in 73% (11/15) of patients receiving ≥1 × 106 CD22-CAR T cells per kg body weight, including 5 of 5 patients with CD19dim or CD19- B-ALL. Median remission duration was 6 months. Relapses were associated with diminished CD22 site density that likely permitted CD22+ cell escape from killing by CD22-CAR T cells. These results are the first to establish the clinical activity of a CD22-CAR in B-ALL, including leukemia resistant to anti-CD19 immunotherapy, demonstrating potency against B-ALL comparable to that of CD19-CAR at biologically active doses. Our results also highlight the critical role played by antigen density in regulating CAR function.

  View details for PubMedID 29155426

• Reduction of MDSCs with All-trans Retinoic Acid Improves CAR Therapy Efficacy for Sarcomas CANCER IMMUNOLOGY RESEARCH Long, A. H., Highfill, S. L., Cui, Y., Smith, J. P., Walker, A. J., Ramakrishna, S., El-Etriby, R., Galli, S., Tsokos, M. G., Orentas, R. J., Mackall, C. L. 2016; 4 (10): 869-880

  Abstract

  Genetically engineered T cells expressing CD19-specific chimeric antigen receptors (CAR) have shown impressive activity against B-cell malignancies, and preliminary results suggest that T cells expressing a first-generation disialoganglioside (GD2)-specific CAR can also provide clinical benefit in patients with neuroblastoma. We sought to assess the potential of GD2-CAR therapies to treat pediatric sarcomas. We observed that 18 of 18 (100%) of osteosarcomas, 2 of 15 (13%) of rhabdomyosarcomas, and 7 of 35 (20%) of Ewing sarcomas expressed GD2. T cells engineered to express a third-generation GD2-CAR incorporating the 14g2a-scFv with the CD28, OX40, and CD3ζ signaling domains (14g2a.CD28.OX40.ζ) mediated efficient and comparable lysis of both GD2(+) sarcoma and neuroblastoma cell lines in vitro However, in xenograft models, GD2-CAR T cells had no antitumor effect against GD2(+) sarcoma, despite effectively controlling GD2(+) neuroblastoma. We observed that pediatric sarcoma xenografts, but not neuroblastoma xenografts, induced large populations of monocytic and granulocytic murine myeloid-derived suppressor cells (MDSC) that inhibited human CAR T-cell responses in vitro Treatment of sarcoma-bearing mice with all-trans retinoic acid (ATRA) largely eradicated monocytic MDSCs and diminished the suppressive capacity of granulocytic MDSCs. Combined therapy using GD2-CAR T cells plus ATRA significantly improved antitumor efficacy against sarcoma xenografts. We conclude that retinoids provide a clinically accessible class of agents capable of diminishing the suppressive effects of MDSCs, and that co-administration of retinoids may enhance the efficacy of CAR therapies targeting solid tumors. Cancer Immunol Res; 4(10); 869-80. ©2016 AACR.

  View details for DOI 10.1158/2326-6066.CIR-15-0230

  View details for Web of Science ID 000385632900007

  View details for PubMedID 27549124

  View details for PubMedCentralID PMC5050151