Genentech, ImmunoGen Win FDA OK for Souped-Up Breast Cancer Drug

Xconomy San Francisco — 

Genentech’s scientists have long wondered about what would happen if they could deliver a more powerful version of their original hit antibody drug for breast cancer. Now they’ll see.

The South San Francisco-based company, a unit of Roche, said today that it won FDA clearance to start selling ado-trastuzumab emtansine (Kadcyla) as a new treatment for breast cancer patients whose tumors have spread, and which overexpress the HER2 protein. The drug, long known as T-DM1, combines the targeting capability of Genentech’s original antibody called trastuzumab (Herceptin) with a toxin that gives it extra tumor-killing punch. The approval is also noteworthy for Waltham, MA-based ImmunoGen (NASDAQ: IMGN), as it licensed technology to Genentech to develop the product, and stands to collect royalties on sales.

The FDA approval of Kadcyla (pronounced kad-SIGH-luh) is an important milestone for patients, for the businesses involved, and for science because of the novel way this drug works. The Genentech drug showed an ability in clinical trials to help women live longer, while causing fewer severe side effects than those who got standard treatment. The drug, priced at $9,800 a month, clearly has the potential to generate billions in annual sales for Genentech for many years to come. For scientists, it represents a major technical achievement, as it’s one of only two marketed drugs that effectively links an antibody to a toxin—the other is brentuximab vedotin (Adcetris) from Seattle Genetics (NASDAQ: SGEN). Researchers hope that these two drugs are just the beginning of a new wave of targeted, and more potent, cancer drugs.

“Kadcyla is an antibody-drug conjugate representing a completely new way to treat HER2-positive metastatic breast cancer, and it helped people in the EMILIA study live nearly six months longer,” said Hal Barron, Genentech’s chief medical officer and head of global product development, in a statement. “We currently have more than 25 antibody-drug conjugates in our pipeline and hope this promising approach will help us deliver more medicines to fight other cancers in the future.”

Genentech showed in its pivotal clinical trial of 991 women that patients on the new breast cancer drug lived a median time of 30.9 months, compared with 25.1 months for those who were randomly assigned to get GlaxoSmithKline’s lapatinib (Tykerb) and Roche’s chemo drug capecitabine (Xeloda). Researchers reported that about 40.8 percent of patients suffered moderate to severe side effects on the new drug, compared with 57 percent in the comparison group.

Still, this is a potent cancer drug, and it does come with some significant side effects. The FDA-approved prescribing information includes a “black box” warns doctors that liver toxicity, heart toxicity and death have occurred in Kadcyla-treated patients. The drug can also cause severe life-threatening birth defects, the FDA said in a statement.

The price is sure to cause some people heartache, too. At $9,800 a month, the price is more than double that of the original trastuzumab (Herceptin), which sells for $4,500 a month. Another Genentech drug approved last year for HER2-positive breast cancer, pertuzumab (Perjeta), was originally priced at $5,900 a month.

Genentech spokeswoman Susan Willson said the company expects a course of therapy with Kadcyla to cost about $94,000, based on patients taking the drug for about 9.6 months. The company is also making the drug available through a patient assistance program for those who can’t afford it, she said. “People who do not have health insurance, or who have reached the lifetime limit set by their insurance company, might qualify to receive Kadcyla for free,” she said.

Genentech tried once before to win FDA approval on the basis of more preliminary, Phase II clinical trial data. The company’s application was turned down in August 2010, as the agency asked for more data. The more definitive proof of Kadcyla’s value came last year in the form of the 991-patient study known as Emilia. About 232,000 women will be diagnosed with breast cancer this year, and an estimated 39,600 will die from it, the FDA said, citing data from the National Cancer Institute.

For more information on the scientific odyssey this drug took to get through the R&D process, see this Xconomy feature from June 2010.