Branched-chain keto acids promote an immune-suppressive and neurodegenerative microenvironment in leptomeningeal disease.

Leptomeningeal disease (LMD) occurs when tumors seed into the leptomeningeal space and cerebrospinal fluid (CSF), leading to severe neurological deterioration and poor survival outcomes. We utilized comprehensive multi-omics analyses of CSF from patients with lymphoma LMD to demonstrate an immunosuppressive cellular microenvironment and identified dysregulations in proteins and lipids indicating neurodegenerative processes. Strikingly, we found a significant accumulation of toxic branched-chain keto acids (BCKA) in the CSF of patients with LMD. The BCKA accumulation was found to be a pan-cancer occurrence, evident in lymphoma, breast cancer, and melanoma LMD patients. Functionally, BCKA disrupted the viability and function of endogenous T lymphocytes, chimeric antigen receptor (CAR) T cells, neurons, and meningeal cells. Treatment of LMD mice with BCKA-reducing sodium phenylbutyrate significantly improved neurological function, survival outcomes, and efficacy of anti-CD19 CAR T cell therapy. This is the first report of BCKA accumulation in LMD and provides preclinical evidence that targeting these toxic metabolites improves outcomes.

Understanding and Managing Large B Cell Lymphoma Relapses after Chimeric Antigen Receptor T Cell Therapy.

Most patients with large cell lymphoma are cured with frontline chemoimmunotherapy. For individuals with refractory disease and those who relapse after conventional therapies, chimeric antigen receptor (CAR) T cells are an important treatment option and have led to remissions in otherwise refractory patients. In the pivotal trials, durable responses were achieved in approximately 40% to 50% of patients treated with axicabtagene ciloleucel, tisagenlecleucel, or lisocabtagene maraleucel, indicating that many patients will require subsequent treatment. Failure after CAR T cell therapy is caused by a variety of factors that can be divided into 3 broad categories: tumor intrinsic factors, other host factors, and inadequacies of the CAR T cells. Within this framework, this article reviews possible mechanisms of treatment failures and, based on the timing of relapse, considers potential salvage therapies and opportunities for future clinical studies.