The news from the European Society for Medical Oncology meeting, or ESMO, came mostly from the large pharmas -- Roche, Merck (NYSE:MRK), and AstraZeneca (NYSE:AZN) in particular -- but a couple of smaller biotechs are benefiting. Shares of Clovis Oncology (NASDAQ:CLVS) and Exelixis (NASDAQ:EXEL) both were up yesterday.

When your partner succeeds
Biotech Exelixis helped develop MEK inhibitor cobimetinib before licensing it to Genentech, which was eventually bought by Roche.

Phase 3 data released at ESMO showed that cobimetinib combined with Roche's Zelboraf helped patients with advanced melanoma that couldn't be removed or had spread to other parts of the body better than Zelboraf alone. The tumors contained a mutation called BRAF V600 that Zelboraf is designed to treat.

Adding cobimetinib to Zelboraf increased median progression-free survival -- the time it takes for the tumor to start growing or for the patient to die (whichever comes first) -- by 3.7 months. The increase might not sound like much, but Zelboraf only produced a 6.2-month progression-free survival, so the increase in 3.7 months was equivalent to reducing the risk of the disease worsening by 49%.

The overall survival data is arguably more important, but hasn't matured enough to be statistically significant. Fortunately, as expected from the delay in progression, it is trending in the right direction with the cobimetinib-Zelboraf combination extending survival more than Zelboraf alone.

A marketing application for cobimetinib has already been submitted to European Union regulators, and Roche plans to file for approval of cobimetinib in the U.S. later this year.

When your competitor "fails"
Clovis' rociletinib is in a race with AstraZeneca's AZD9291 to be approved to treat lung cancer in patients whose tumors have developed mutations that make them resistant to current treatments.

Data released at ESMO showed that AZD9291 produced progression-free survival of 9.6 months. But four months ago at the American Society of Clinical Oncology meeting, Clovis said progression-free survival for patients taking rociletinib was at least 12 months; not enough of the patients had progressed or died for the true median to be calculated at that time.

While 12-plus months is clearly longer than 9.6 months, there are a couple of caveats here. Clovis' data covered just 40 patients, while AstraZeneca's data contained approximately the same data set size (30% of 138 enrolled patients). Neither trial had a control group, which makes it challenging to compare the two progression-free survival numbers.

Investors shouldn't be calling a winner on these early data. My guess is that Clovis' stock spike was a bit of a relief rally from investors who were worried that the ESMO data would show that AZD9291 handily beat rociletinib.

PD-1 pathway still dominates
For more than a year, inhibitors of the PD-1 pathway have been a major story of every cancer meeting, and ESMO was no different.

Merck presented data for its PD-1 drug Keytruda in patients with advanced bladder cancer and advanced gastric cancer. In bladder cancer, Keytruda produced a response in 24% of the 29 patients who received the drug. In gastric cancer, 31% of 39 patients responded.

While the numbers are small, these are advanced patients, so any response is good news. Keytruda was recently approved in the U.S. to treat melanoma, but expanding into other cancers is key for the drug to reach its full potential.

Bristol-Myers Squibb's (NYSE:BMY) rival drug, Opdivo, is in hot pursuit with marketing applications recently submitted to the FDA and to EU regulators. At ESMO, Bristol-Myers Squibb presented phase 3 data in which Opdivo produced a response in 32% of patients with advanced melanoma, handily beating chemotherapy that only produced an 11% response rate in the control group.

AstraZeneca's inhibitor of the PD-1 pathway, MEDI4736, is further behind Keytruda and Opdivo, but early indications suggest combining it with tremelimumab might make for a safer treatment than Bristol-Myers Squibb's drug plus Yervoy.

Brian Orelli has no position in any stocks mentioned. The Motley Fool recommends Exelixis. Try any of our Foolish newsletter services free for 30 days. 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.