Experimental cancer drugs effective – but with drawbacks

Two emerging technologies look promising, but top oncology researchers are concerned about dangers seen during clinical trials.

In some trials two new approaches have eliminated all traces of blood cancers in 40% to 90% of patients who had no remaining options. (Eric Gaillard, Reuters)

A new wave of experimental cancer drugs that directly recruit the immune systems powerful Tcells are proving to be immensely effective weapons against tumours, potentially transforming the $100-billion global market for drugs that fight the disease.

But top oncology researchers are concerned about the two emerging technologies, citing dangers seen repeatedly in clinical trials including the potentially fatal buildup of toxic debris from killed tumour cells and damage to healthy tissue. Such side effects could block regulatory approval if they arent controlled, say researchers and drug company executives.

In some trials, the two new approaches, known as CAR T cells and bispecific antibodies, have eliminated all traces of blood cancers in 40% to 90% of patients who had no remaining options.

The drugs could reap annual sales in the tens of billions of dollars for their manufacturers, especially if they can also eliminate solid tumours in such terminally ill patients.

CAR T cells, or chimeric antigen receptor T cells, are T cells that have been removed from the body and attached through genetic engineering to an antibody fragment that recognises a specific tumour protein.

T cells are an especially powerful disease-fighting kind of white blood cell. The result is a drug with the killing power of a greatly enhanced T cell, combined with the tumour-spotting ability of an antibody.

Bispecific antibodies are a twist on conventional antibodies, Y-shaped proteins whosetwo arms grasp for the same protein target found on cancer cells.

With bispecifics, one arm of the antibody typically grasps a cancer cell while the other arm takes hold of T cells, bringing the mortal enemies into contact. The T cell punches holes into the adjacent tumour cell and injects deadly enzymes. Conventional antibodies, by contrast, dont directly recruit T cells.

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Experimental cancer drugs effective - but with drawbacks