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Source: U.S. Food and Drug Administration. 

The World Health Organization identified more than 14,000 disease, disorders, and ailments in 2011, but none continues to garner more attention from drugmakers than cancer.

In 2014, global cancer drug sales hit $100 billion for the first time, according to IMS Health, with forecasts calling for global sales growth of another 17% to 47% by 2018. Oncology is a fast-growing space, and drug developers want their share of the pie.

Even more importantly, there's still plenty of research left to be done to cure cancer. Don't get me wrong, we've seen marked survival improvements in breast cancer and prostate cancer, the two most-common cancer types, according to data from the American Cancer Society. However, new therapies are still needed in dozens of cancer types that have only seen marginal improvements over the last four decades.

The potentially good news for patients is that the Food and Drug Administration could approve as many as three cancer therapies in October, providing potentially new options to certain cancer patients. Let's have a brief look at these three upcoming FDA decisions and dissect the likelihood of an approval.

Can Keytruda expand?
On Oct. 2, 2015, the FDA is expected to make its decision as to whether or not to expand the label of Keytruda, a cancer immunotherapy developed by Merck (NYSE:MRK), to include patients with advanced non-small cell lung cancer.

Keytruda
Source: Merck.

Cancer immunotherapies work by enhancing the body's immune system to be more efficient at locating and fighting cancer cells. Keytruda, a checkpoint inhibitor of PD-1, is already approved as a treatment for BRAF V600 mutation-positive advanced melanoma, and I suspect it's well on its way to an expanded label in advanced NSCLC following a successful clinical trial.

In April, Merck released encouraging results from its phase 1 study involving advanced NSCLC patients. The 495-patient trial yielded a response rate of 45% in patients that expressed high levels of PD-L1, while the response rate for low-to-moderate PD-L1 expression was 16.5%. Considering that rival checkpoint inhibitor Opdivo from Bristol-Myers Squibb already had its label expanded by the FDA with a similar overall response rate of 19%, and both have demonstrated similar safety profiles, it seems only logical that the FDA may green light Keytruda in advanced NSCLC as well.

With the global immunotherapy market expected to tip the scales at $35 billion by 2023, Keytruda looks well on its way to nabbing a sizable chunk of this growth.

Is an MM-398 approval in the cards?
If at first you don't succeed, dig your heels in the dirt and keep pushing until you do. This should be Merrimack Pharmaceuticals' (NASDAQ:MACK) modus operandi after its shareholders suffered through three miserable failures with MM-121, an experimental cancer therapy that failed in breast, lung, and ovarian cancer. MM-121 had been Merrimack's lead therapy for some time, even netting it a collaborative deal with Sanofi, but it wasn't meant to be.

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Source: National Cancer Institute.

Written off for dead, Merrimack responded with MM-398, a treatment for pancreatic cancer that has a PDUFA decision date of Oct. 24, 2015. Among cancer types, few offer a more discouraging long-term survival rate than pancreatic cancer. Merrimack's MM-398 didn't cure patients' pancreatic cancer in the NAPOLI-1 trial, but it did demonstrate a more durable response that led to a statistically significant improvement in median overall survival. Overall median survival for the MM-398 arm in combination with 5-fluorouracil and leucovorin rose to 6.1 months from 4.2 months in the control arm without MM-398.

As my Foolish colleague Todd Campbell pointed out last year, Merrimack's MM-398, which is newer form of irinotecan, a component of the folfiri chemotherapy cocktail that can be quite potent against tough-to-treat cancers but also has high toxicity rates, is looking to displace convention irinotecan in the folfiri regimen if it's approved.

Will an approval come? Considering that statistically significant overall survival improvements are few and far between in pancreatic cancer, and that the safety profile of both arms was similar, I'd have to say the pendulum is certainly swinging in MM-398's favor. However, with Merrimack boasting a $1.2 billion valuation, an approval may already be baked into the cards.

Will Amgen claim victory with its immunotherapy?
Perhaps the most intriguing potential approval comes from Amgen (NASDAQ:AMGN) with its cancer immunotherapy, talimogene laherparepvec (also known as T-Vec).

Amgen Flickr
Source: Amgen via Flickr.

T-Vec is a reengineered herpes simplex virus designed to replicate inside cancer cells to make them burst. In addition, it draws the attention of the immune system, eliciting a response. Specifically, T-Vec is being targeted as a treatment for advanced melanoma, although combining the drug with other cancer immunotherapies and/or tackling other cancer indications does seem to be in the cards if T-Vec wins approval from the FDA on or before its PDUFA decision date of Oct. 27, 2015.

Unlike Keytruda and MM-398 which had clear cut success, T-Vec's path has been a bit bumpier. In phase 3 studies T-Vec met its primary endpoint of a durable response in advanced melanoma patients, but it unexpectedly missed a key secondary endpoint: a statistically significant improvement in median overall survival. The company noted in its top-line data release that the trend clearly favored the T-Vec arm in terms of survival, but the survival trend wasn't statistically significant. That's a bit worrisome considering that other advanced melanoma therapies have shown a statistically significant advantage in median overall survival.

So, is T-Vec doomed? Before the FDA advisory committee meeting I wouldn't have been able to suggest either way how the FDA might rule. However, following its meeting and the 22 to one suggestion that T-Vec be approved, I'm now leaning in the direction that it'll be approved by the FDA. The regulatory body isn't required to follow the suggestion of its advisory board, but it typically does.

But, it's worth noting that the advanced melanoma space is now getting crowded, and potentially more intriguing options may be available in terms of survival. In short, T-Vec may not offer a huge top- or bottom-line boost for Amgen. However, getting that initial foot in the door with an approval should open the door for T-Vec to strike a plethora of combination opportunities.

Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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