What happened

Shares of Agenus (NASDAQ:AGEN), a clinical-stage immuno-oncology company, jumped 51.6% in November, according to data from S&P Global Market Intelligence. A solid third-quarter report and a clinical trial failure from AstraZeneca (NYSE:AZN) pushed up the stock.

So what 

Agenus' vaccine booster is a part of Shingrix, a new shingles vaccine that GlaxoSmithKline (NYSE:GSK) launched late last year. Sales of the vaccine exceeded expectations and reached an annualized $1.5 billion run rate during the third quarter.

Agenus signed away its royalty percentage for the blockbuster vaccine in return for $190 million earlier this year, but part of its deal with Healthcare Royalty Partners includes a $25.9 million clawback that Agenus won't need to pay. It also looks as if Agenus has a shot at collecting $40.4 million in milestone payments if Shingrix sales achieve an annualized run rate of $2.75 billion.

Money arranged in the shape of an upward sloping chart.

Image source: Getty Images.

Agenus also perked up after AstraZeneca announced dismal pivotal trial results with two checkpoint inhibitors. Imfinzi and tremelimumab are drugs that inhibit immune checkpoint inhibitors PD-1, and CTLA-4, respectively. Agenus has similar candidates ready for late-stage testing, and investors were pleased to see that Astra's combo probably won't be a competitive threat.

Now what

There's already an anti-CTLA-4 and at least half-a-dozen PD-1 checkpoint inhibitors already approved in the U.S., so Agenus will have a hard time finding a partner willing to pay for costly late-stage trials. That's going to be a problem for Agenus, because it finished September with just $46 million in cash and cash equivalents after losing $112 million during the first nine months of the year.

Agenus will probably earn some milestone payments here and there from a handful of collaboration partners, but shareholders should remain braced for another value-diluting share offering in the quarters ahead.

Cory Renauer has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.