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Exelixis Goes for It

By Brian Orelli, PhD – Oct 13, 2016 at 4:50PM

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The biotech plans to expand the potential patient pool for Cabometyx, but the plan isn't without complications.

Image source: Exelixis.

Exelixis (EXEL -1.40%) started the marketing stage of its company life with a whimper. Last year in its third full year on the market, the biotech managed sales of just $37.2 million for Cometriq -- not surprising given the drug is only approved for metastatic medullary thyroid cancer, a relatively rare disease.

But Exelixis is looking to progress with a bang. Earlier this year, Cabometyx, which has the same active ingredient as Cometriq, was approved as a second-line treatment for kidney cancer. The biotech recorded sales of $31.6 million for the two drugs in the second quarter -- almost as much as it brought in all of last year. And this week, Exelixis announced plans to expand the potential market for Cabometyx in kidney cancer, going after a first-line indication in patients who have intermediate- or poor-risk disease.

The biotech is rolling the dice a little because the clinical trial showing that Cabometyx works in the first-line setting -- that is, previously untreated patients -- wasn't really designed to get the drug approved. The so-called CABOSUN trial was a phase 2 trial really only designed to figure out if going after the first-line treatment was worth it.

But the data was so good that Exelixis feels confident that the Food and Drug Administration (FDA) will approve the expanded indication. Cabometyx kept patients alive while keeping their tumors from growing for a median of 8.2 months compared to 5.6 months for Pfizer's (PFE -1.60%) Sutent, the current standard of care. Put another way, there was a 31% reduction in the rate of disease progression or death for patients taking Cabometyx compared to Pfizer's drug.

The secondary endpoints looked promising, as well, with 46% of patients responding to Cabometyx compared to 18% of patients taking Pfizer's Sutent. Overall survival also favored Cabometyx with a median of 30.3 months compared to 21.8 for Sutent, although the difference wasn't statistically significant -- not surprising given the smaller numbers of patients who had progressed that far.

The FDA may be worried that the progression and response rates were assessed by investigators who may be biased, and the individual assessments could also introduce some variability into the data. To alleviate those potential issues, Exelixis plans to perform an independent review of the images of the patients' tumors by a centralized committee.

Exelixis' European partner Ipsen is talking to regulators in Europe to discuss the potential of submitting the same data to the overseas agency.

More patients, higher sales

Expanding from a second-line indication into first-line patients with intermediate- or poor-risk disease should help Cabometyx sales, because only about 60% of the patients end up being treated with a second drug. The rest either die while on the first drug, or are too sick to take a second therapy.

While the FDA might be happier with statistically significant overall survival data from a larger trial, regulators will hopefully be content enough with the current dataset to approve the expanded indication knowing that 40% of patients won't have the opportunity to take Cabometyx if it's not approved for the first-line setting.

From Exelixis's standpoint, rolling the dice with the current data also makes sense because the larger first-line indication that includes lower-risk patients is evolving quickly. It seems likely that patients will eventually be treated with a combination of drugs -- potentially Cabometyx and Bristol-Myers Squibb's Opdivo -- so running a large phase 3 trial comparing Cabometyx monotherapy to Sutent, doesn't make much sense.

Exelixis hasn't given guidance as to when an approval for first-line kidney cancer patients might occur, but it seems safe to assume it'll take at least a few months to complete the independent review, and then another six months for the FDA review of the application. In the meantime, Cabometyx may benefit from some off-label sales from doctors who were impressed with the CABOSUN data.

Brian Orelli has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Exelixis. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.

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