‘Goldilocks’ treatment window could lead to cancer therapy without harmful side-effects

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A team of Australian-Israeli researchers have developed a way to potentially reduce the toxic side-effects of a type of immunotherapy, in findings that could overcome the pioneering treatment’s biggest limitation.

CAR-T cell therapy is a relatively new form of immunotherapy that enhances a patient’s killer immune cells to attack and eliminate cancer.

It can be up to 90 per cent effective in certain blood cancers and can even deliver long-term remissions and cures in some patients. However, a significant limitation is the treatment’s potentially harmful side effects, with approximately 50 per cent of patients experiencing dangerous complications.

The new study, led jointly by WEHI researchers in collaboration with Israel’s Weizmann Institute of Science, has designed a way to identify a ‘goldilocks’ window that strikes a balance of safety and efficacy.

The team’s approach fine-tunes the cells used in the immunotherapy so that their activity is strong enough to eliminate the cancer but not so strong that they generate toxic side effects. The findings, led by WEHI’s Associate Professor Matthew Call and Associate Professor Melissa Call, are published in eLife.

CAR-T cell therapies involve collecting T cells from a cancer patient and supercharging the cells by individually re-engineering them in the laboratory. These enhanced cells are then put back into patients.

The T cells are engineered to produce proteins on their surface called chimeric antigen receptors (CARs), which act as artificial sensors that enable T cells to recognise and bind to specific proteins on the surface of cancer cells more efficiently.

Associate Professor Matthew Call said this synthetic sensor is what gives T cells the enhanced ability to attack and eliminate threats, like cancer cells.

“While putting these supercharged T cells into a patient with a high tumour burden can swiftly eradicate cancer cells, it also creates the perfect storm for an ongoing toxic response that can be harmful,” said Associate Professor Call.

There is currently no way of reliably predicting how strong CAR-T cell therapy will be for a patient. While previous studies have attempted to fine-tune T cells by targeting the end sections of the sensor, which either bind to the cancer cell or instruct the T cells to kill, the new research is the first to look at completely redesigning the middle part.

Researchers leveraged the computational expertise of the Weizmann Institute of Science to stitch together pieces of natural immune sensors with custom-designed synthetic elements, to generate new circuits that could be used to tune and assess variations of potency.

“Focusing on the connector fragment in the middle allows us to generate different versions of CARs that we know are stronger or weaker, enabling us to customise them to a patient’s potency requirements,” continued Associate Professor Call.

“Being able to predictably tune this T cell activity significantly broadens our research, contrary to previous studies, because we are targeting something that exists in every immunotherapy scenario.

“For the first time, we can establish rules that will be applicable to any cancer where CAR-T cell immunotherapy is being used.”

There are currently over 600 clinical trials of CAR-T cell immunotherapy, with the treatment already being used for several blood cancers.

Researchers say they hope their new tool could be used to triage immunotherapy patients based on the level of potency they require in early phases of their treatment and bring the field closer to striking that ‘goldilocks’ treatment window for many different cancers.

The next research phase, supported by the NHMRC, the Leukaemia Foundation, Cancer Australia and Hearts and Minds Investments and TDM Foundation will focus on progressing these findings into a clinical setting to see CAR T cell therapy used as a safer, first-line treatment.