Engineered cell cross-talk unlocks CAR-T potential against glioblastoma

A team of researchers from the San Raffaele-Telethon Institute for Gene Therapy (SR-TIGET, Milan), led by Nadia Coltella and Luigi Naldini, has unveiled a powerful strategy to rejuvenate the effectiveness of chimeric antigen receptor (CAR) T cell therapy against glioblastoma, one of the most lethal and treatment-resistant brain tumors. The findings, published in Science Translational Medicine, highlight how gene therapy targeting immune stimulating cytokines to the tumor microenvironment (TME) and enabling their private cross-talk with CAR-T cells not only restores CAR-T killer activity but also boost a broader immune response that inhibits tumor growth and extends host survival in a preclinical glioblastoma models.

The study builds on the prior development by the Naldini's laboratory of a gene therapy strategy that exploit genetic engineering of hematopoietic progenitors to generate a progeny of monocyte/macrophages that selectively release their immune stimulating payload upon infiltrating a tumor. This strategy has been taken to its first-in-human clinical testing as stand-alone treatment of glioblastoma by the biotech company Genenta Science, a spin-off from the San Raffaele Institute now listed on the NASDAQ.

“Solid tumors like glioblastoma have been notoriously difficult for CAR-T cells to penetrate and control,” explains Dr. Rossari, first author of the work, “By reprogramming a population of tumor-infiltrating macrophages to deliver cytokines directly into the tumor, we’ve morphed the immunosuppressive TME into one supportive of immune cells, thus allowing CAR T cells to better persist, become activated and attack tumor cells.”

CAR-T cells have shown transformative results in blood cancers but have struggled in solid tumors due to the hostile, immunosuppressive TME. The team’s strategy leads to selective release of two cytokines within the TME: interferon-α (IFN-α), a pleiotropic immune stimulator that counteracts local immune suppressive cues and enforces antigen presentation and immune effectors’ activity, and an engineered mutant of interleukin-2 that can only activate a cognate mutant receptor co-introduced with the CAR into T cells, thus boosting the proliferation specifically of the administered effector engaged in fighting the tumor.

“The private ‘cross-talk’ between genetically engineered macrophages and CAR T cells established in the TME ensures that the immune stimulants act only where needed, sparing the rest of the body from systemic toxicity, and specifically on the relevant target cells involved in the tumor attack, again preventing collateral damage and aberrant effects,” says Dr. Alvisi, co-first author of the study.

In a mouse model of glioblastoma that mimics the pathology and immunological barriers seen in human patients, the targeted cytokines rescued the activity of CAR-T cells that, given alone, were ineffective – as mostly seen in clinical trials. In turn, the rescued CAR T cells now synergized with cytokine delivery, significantly enhancing their effect on delaying tumor growth and extending mouse survival. Strikingly, even tumors with only a fraction of cells expressing the CAR-targeted antigen B7-H3 were effectively controlled, indicating engagement of endogenous T cells on top of the CAR-T to fight the tumor.

“We observed not only reactivation of the CAR-T cells but also the recruitment of the host’s own T cells against a wider range of tumor antigens,” says Dr. Nadia Coltella, senior co-corresponding author. “This phenomenon, known as antigenic spreading, was mostly dependent on IFN-α activity in the TME and is a key feature for creating effective immunity as it may overcome immune evasion by tumors targeted only through a single antigen by the CAR-T cells.”

“This work represents another important step forward in our decade-long commitment to develop a novel gene and cell therapy strategy effective against tumors, as we have been able to do for several genetic diseases along the life of our institute” adds Luigi Naldini, Director of SR-TIGET and Professor at Università Vita-Salute San Raffaele. “The tumor-targeted IFN-α delivery strategy is already being evaluated as stand-alone treatment in a first-in-human phase 1/2a trial on the most aggressive type of glioblastoma (Temferon trial) led by the biotech company Genenta Science. The study has shown feasibility, safety, biological activity in reprogramming the TME and early but promising indication of therapeutic benefit, albeit limited by the small number of treated patients and the design of a phase 1 study. A combination of Temferon with CAR-T cells administration, as prompted by our new study, could in future further enhance the benefit of the treatment and broaden its efficacy to a larger fraction of patients.”

This study was supported also by the Italian Association for Cancer Research (AIRC), the Louis-Jeantet Foundation through the Jeantet-Collen Prize for Translational Medicine to Luigi Naldini, and a research contract from Genenta Sciences.