There are more promising cancer treatments in development now than at any other point in human history. That's great news for cancer patients. It's also good news for investors looking for stocks with significant potential.

Three cancer drug stocks in particular could be huge winners for investors: Agios Pharmaceuticals (NASDAQ:AGIO), Celldex Therapeutics (NASDAQ:CLDX), and Clovis Oncology (NASDAQ:CLVS). Here's why these stocks could make you rich over time.

An assortment of pills and a hand holding a syringe, on top of a paper with "cancer" written at the top, and a stethoscope lying on it.

Image source: Getty Images.

Agios Pharmaceuticals: Promising leukemia drugs and a big partner

Some investors have already gotten at least a little wealthy with Agios. The stock is up more than 30% so far in 2017.

The big story for Agios is experimental IDH2 inhibitor enasidenib. Celgene (NASDAQ:CELG) partnered with Agios on the drug in 2010. The big biotech filed for U.S. approval of enasidenib in treating relapsed or refractory acute myeloid leukemia (AML) with an IDH2 mutation in late December. The U.S. Food and Drug Administration recently granted priority review for the drug. A decision is expected by Aug. 30. 

Agios also has another promising pipeline candidate, ivosidenib, for which it owns full commercialization rights. The drug inhibits mutant IDH1 proteins. Agios expects to submit ivosidenib for FDA approval for treatment of relapsed or refractory AML with an IDH1 mutation by the end of this year. The company also is initiating a late-stage study of the drug in combination with Celgene's Vidaza in newly diagnosed AML patients.

Celldex Therapeutics: Rising from the ashes

Investors haven't been so lucky with Celldex thus far. The stock took a beating early last year, when experimental glioblastoma vaccine Rintega flopped in a late-stage study. However, that failure didn't end the possibility of success for Celldex.

The biotech claims a couple of other promising cancer drug candidates. Glembatumumab vedotin (glemba) is in a registrational phase 2 study targeting treatment of triple-negative breast cancer. Celldex expects to complete enrollment in September. If all goes well, the biotech could potentially launch glemba in 2019.

Celldex's other key pipeline candidate is varlilumab, also known as varli. The biotech is evaluating varli in combinations with glemba, Opdivo, and Keytruda in a phase 2 study for treatment of metastatic melanoma. Celldex is also collaborating with Bristol-Myers Squibb in a phase 2 study of varli in combination with Opdivo as a treatment for multiple types of cancer. 

Clovis Oncology: Racing with Rubraca

Clovis Oncology has been the biggest winner of these three cancer drug stocks over the past 12 months. The biotech's shares have more than quadrupled since April 2016.

Clovis is the only company in the group to already have an approved product. Rubraca won FDA approval as a third-line treatment for ovarian cancer in December 2016. Because the FDA approval in ovarian cancer was an accelerated approval, Clovis must conduct a confirmatory study. 

Rubraca is also being evaluated in clinical studies exploring the potential for treating other indications. Clovis has a late-stage trial in progress targeting prostate cancer. Several other phase 2 investigator-initiated trials are under way evaluating Rubraca in treating breast cancer, and gastroesophageal cancer. Some analysts think the drug could reach peak annual sales of close to $1 billion. That estimate could increase if Rubraca wins approval for additional indications beyond ovarian cancer.

Best bet

Celldex Therapeutics could be the biggest winner of the three cancer drug stocks if glemba and varli are successful. However, Celldex also has the most risk with a pipeline that isn't as far advanced as Agios or Clovis.

Agios Pharmaceuticals is in a better position. The partnership with Celgene on enasidenib is a major plus. 

I like the prospects for Clovis Oncology best of all, though. The biotech does face competition. Tesaro recently won approval for its Zejula in treating ovarian cancer.  AstraZeneca could also soon join the fray. However, the safety and efficacy profile for Rubraca should give it an edge over these rivals. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.