This Cancer Drug Works, but Indication Drama Remains

Roche and ImmunoGen's (NAS: IMGN) T-DM1, now called trastuzumab emtansine, works. Still. Let's hope the Food and Drug Administration accepts the marketing application this time.

Roche applied for an accelerated approval of trastuzumab emtansine back in 2010 using phase 2 data. The accelerated approval program allows drugs to be approved with less data -- phase 2 is usually sufficient -- but is only available for patients who don't have any other options. The FDA decided that the breast cancer patients Roche tested in the phase 2 trial had other options, so the agency refused to even look at the marketing application.

Fast-forward to today. Roche said its phase 3 trial pitting trastuzumab emtansine against a combination of Xeloda, which it sells, and GlaxoSmithKline's (NYS: GSK) Tykerb passed one of its two clinical endpoints. Breast cancer patients who had already failed Roche's Herceptin and a taxane, such as Bristol-Myers Squibb's (NYS: BMY) Taxol, Sanofi's (NYS: SNY) Taxotere, or Celgene's (NAS: CELG) Abraxane, "lived significantly longer without their disease getting worse" -- called "progression-free survival" in scientific terms.

Roche is saving the numbers for a scientific meeting, and it didn't release data on the other endpoint, overall survival, because the data "are not yet mature" -- a polite way of saying enough patients in the trial haven't died yet. But assuming Roche isn't embellishing the data, it seems likely trastuzumab emtansine will be approved after the company applies to regulatory agencies later this year.

ImmunoGen will get a royalty on trastuzumab emtansine once it's on the market because it contributed the emtansine part of the molecule, a toxic payload attached to Roche's Herceptin (trastuzumab).

While this data is important for getting the drug on the market, it'll be data from a trial in first-line breast cancer patients that's most important for capturing most of Herceptin's $5.8 billion market. Roche is running a trial in that population comparing trastuzumab emtansine with or without another drug under FDA review, pertuzumab, to Herceptin plus a taxane.

To justify ImmunoGen's market cap, which is a little larger today after the positive results, the first-line trial needs to work and some of the other products being developed using ImmunoGen's toxic payload technology need to come to fruition as well. Fortunately, today's results should give investors a little more confidence that the technology is working.

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At the time thisarticle was published Fool contributor Brian Orelli holds no position in any company mentioned. Click here to see his holdings and a short bio. Motley Fool newsletter services have recommended buying shares of GlaxoSmithKline and Immunogen. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.

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