Arguably, all drug-development events during the year bear significance, but there may be no event more closely monitored by investors, patients, and physicians than the American Society of Clinical Oncology's (ASCO) annual meeting, which will be held in early June.

Drug developers increase their focus on cancer immunotherapies

Over the last three-plus decades, we've witnessed major advancements in how drug developers are treating cancer. For instance, the two most commonly diagnosed cancer types, prostate cancer and breast cancer, now have five-year survival rates in the 90-percentile, which is up substantially from 1975-1977, when five-year survival rates for prostate and breast cancer was 68% and 75%, respectively, according to the American Cancer Society.

On top of major survival improvements, global oncology sales topped $100 billion in 2014, and based on estimates from IMS Health, global sales could grow to as much as $147 billion by 2018. Thus, drug developers have an added interest in exploring oncology-based therapeutics because the profitability of these drugs can fuel research into additional oncology, chronic condition, or rare-disease research.

Image source: Bristol-Myers Squibb.

Without question, cancer immunotherapies have been the most exciting thing on pharmacy shelves to treat cancer during the past two years. Cancer immunotherapies are injectable drugs that work by supercharging your immune system to locate and destroy cancer cells. When used in combination with chemotherapy or other existing cancer drugs, the results have been phenomenal.

There are two key players in the immunotherapy field right now. The first is Merck's (NYSE:MRK) Keytruda, which is approved to treat first- and second-line advanced melanoma, as well as second-line advanced non-small-cell lung cancer (NSCLC) in patients with high levels of PD-L1 expression.

The second is Bristol-Myers Squibb's (NYSE:BMY) Opdivo, a treatment for advanced melanoma, second-line advanced NSCLC (regardless of PD-L1 expression), and second-line advanced renal cell carcinoma. Both companies released intriguing abstract data ahead of ASCO earlier this week, and as such have taken center stage.

These pre-ASCO cancer abstracts stole the show

Image source: Merck.

Merck was perhaps the biggest beneficiary of the two, with the release of two abstracts detailing much-improved survival rates for patients taking Keytruda. In a study detailing long-term survival data for patients with advanced melanoma, some 55% taking Keytruda were still alive at the three-year mark, which compares favorably to Bristol-Myers Squibb's Yervoy, which had a three-year survival rate of 43%. Prior to the emergence of cancer immunotherapies, the majority of advanced melanoma patients passed away in less than a year, so this is a major improvement in patient survival and quality of care. Keytruda continues to maintain dominant market share in the advanced melanoma indication.

The second abstract detailed survival data from the KEYNOTE-021 study, which tested Keytruda in combination with chemotherapy in 74 front-line advanced NSCLC patients. The results demonstrated a 10-month progression-free survival benefit overall, and a 14-month to 15-month benefit in patients with PD-L1-expressing tumors. Keytruda has been playing second fiddle to Opdivo in second-line NSCLC due to its more-confined treatment parameters -- only high PD-L1-expressing patients -- but this data could certainly turn some heads.

Bristol-Myers Squibb also came out with an encouraging abstract of its own ahead of ASCO. The release of two-year survival data for CHECKMATE-017 and CHECKMATE-057 from two phase 3 trials involving Opdivo versus docetaxel in previously treated advanced NSCLC showed a discernable benefit versus the placebo. In CHECKMATE-057 for non-squamous NSCLC, 29% of patients taking Opdivo were still alive compared to just 16% on docetaxel. In CHECKMATE-017 for squamous NSCLC, the survival benefit was nearly triple (23% on Opdivo versus 8% on docetaxel).

Keep an eye on these immunotherapy products, too

In addition to these established players, there are a number of clinical or green-behind-the-ears immunotherapy treatments that are going to be worth eyeing during ASCO.

Image source: Roche. 

One immunotherapy you'll want to monitor closely is Tecentriq -- previously known as atezolizumab -- from Roche (OTC:RHHBY). Tecentriq was approved to treat bladder cancer on Wednesday by the Food and Drug Administration after eliciting tumor shrinkage in 14.8% of patients, which had a durable response of between 2.1 months and 13.8 months, and eliminating the cancer in 5.5% of patients.

Roche's immunotherapy product is being tested in a number of cancer types and combinations. As the clear leader in oncology research with dozens of ongoing clinical oncology studies (not just for immunotherapies), it will be wise to pay attention to what data Roche reveals on Tecentriq at ASCO.

Pfizer (NYSE:PFE) and Merck KGaA (OTC:MKGAY) will also be unveiling data for their cancer immunotherapy avelumab. One abstract, in particular, that investors may want to pay attention to is the phase 1b JAVELIN study involving avelumab as a first-line treatment for advanced NSCLC.

Among 75 patients, the unconfirmed overall response rate was 18.7%, and stable disease was reported in 45.3% of patients. It will be interesting to see how this data fares relative to Keytruda, Opdivo, and other immunotherapies, especially considering that Pfizer paid Merck KGaA a veritable arm and leg to get its hands on avelumab -- $850 million upfront, $2 billion in possible milestone payments, and part of its Xalkori revenue stream.

Long story short, ASCO is once again going to be a big driver of oncology-based drug developers' stock valuations come June, and it's going to be worthwhile for investors to pay close attention to what abstracts Big Pharma chooses to highlight. All eyes are on cancer immunotherapies, and yours should be, too.