AstraZeneca's Lynparza slowed the progression of breast cancer caused in part by mutations in the BRCA gene, an inherited condition that causes up to 3% of all breast cancers. These cancers are particularly hard to treat, and some women who test positive for BRCA genes opt for double mastectomies in order to lower their risk.
In a study of 302 women whose breast cancer had spread, Lynparza reduced the risk of cancer growing significantly by 42% compared to chemotherapy, with fewer side effects. Tumors shrank in 60% of the patients who received Lynparza, versus 29% of those who got chemo. Women who received Lynparza went seven months before their cancer grew enough that doctors said it progressed, compared to 4.2 months for those on chemo. Serious side effects occurred in 50% of the women who received chemotherapy, versus 37% of those who received Lynparza.
Mutations in the BRCA gene, like the ones that led actress Angelina Jolie to opt for a mastectomy, raise the risk of cancer because they make the body less likely to repair damage to its DNA, making the mutations that lead to tumors more likely. Lynparza is one of a much-watched class of medicines called PARP inhibitors that further muck up cells' ability to repair DNA. This hurts cancer cells more than healthy ones. But it may mean that Lynparza only works in cancers where BRCA mutation plays a role.
Lynparza is already approved for ovarian cancer that is caused by BRCA, as are two other drugs called Zejula, made by a small firm called Tesaro, and Rubraca, from a second small company called Clovis Oncology. Last year, Lynparza generated $218 million in sales, a figure Bernstein Research analyst Timothy Anderson forecasts will grow to $684 million by 2020, in part because of the breast cancer success. A study in pancreatic cancer will read out next year, and one in prostate cancer in 2020.
Getting breast cancer results is good for Astra, but the result could also be important for those companies because investors will also take it as evidence that the other drugs will prove effective. The big question is whether any of these medicines has a competitive edge. The field has become very hot. Shares in Clovis and Tesaro are both up more than 200% over the past 12 months, and another PARP inhibitor played a key role in Pfizer's $14 billion purchase of the biotechnology firm Medivation last year.