Bristol-Myers Squibb (BMY - Get Report) and Nektar Therapeutics (NKTR - Get Report) have formed a research collaboration looking for a way to increase the number of cancer patients who can benefit from immunotherapy.

At this point, the cancer partnership between the two companies is purely scientific. No money is changing hands.

Bristol and Nektar will share the costs equally to conduct a series of clinical trials enrolling patients with multiple types of cancer. The patients will be treated with a combination of Bristol's approved PD-1 checkpoint inhibitor Opdivo and Nektar's NKTR-214, an experimental drug designed to stimulate the growth of cancer-killing T cells, the companies said Tuesday.

PD-1 checkpoint inhibitors like Opdivo work by releasing a molecular brake used by tumors to prevent T cells from recognizing and killing cancer cells. These new drugs are very effective, but only in a minority of patients with "hot" tumors already studded with cancer-killing T cells.

Bristol-Myers Squibb is a holding in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells BMY? Learn more now.

Unfortunately, a majority of patients have tumors that are "cold," meaning they lack sufficient numbers of T cells needed to kill cancer cells even when checkpoint inhibitors release the brake.

This is where Nektar's NKTR-214 might help, by stimulating the presence of T cells in and around tumors. If NKTR-214 can convert "cold" tumors to "hot" (or at least make them immunologically warm), combination therapy with checkpoint inhibitors like Opdivo might be more effective, said Nektar Chief Scientific Officer Steve Doberstein in a phone interview Monday.

A Bristol representative was not available for comment on the partnership. Bristol-Myers Squibb is a holding in Jim Cramer's charitable Action Alerts PLUS portfolio.

The Opdivo/NKTR-214 clinical trials to be conducted by Bristol and Nektar will enroll patients with four types of cancer -- kidney, melanoma, non-small cell lung and bladder -- already susceptible to elimination by checkpoint inhibitors used on their own. Adding NKTR-214 to the treatment could boost the number of patients who respond, or help them respond longer.

A fifth clinical trial will test the Opdivo/NKTR-214 combination in patients with colon cancer. Colon cancer has so far proven to be relatively resistant to checkpoint inhibitors, but the addition of NKTR-214 might change that.

For Bristol, the research pair-up with Nektar is one of dozens of combination drug approaches -- Opdivo plus (fill in the blank) -- aimed at boosting the efficacy of its cancer immunotherapy. The other main goal, of course, is to grow sales.

Bristol reported Opdivo sales of $1.5 billion in the first half of 2016. The company competes for checkpoint inhibitor sales with Merck (MRK - Get Report) and Roche  (RHHBY) today. AstraZeneca (AZN - Get Report) is expected to enter the market soon.

At this point, Nektar is a speck in the cancer immunotherapy world compared to Bristol, so the new collaboration helps put NKTR-214 on the map and could accelerate the drug's development, depending on the outcome of the combination studies.

On its own, Nektar is conducting a phase I study of NKTR-214 in multiple tumor types, with interim results to be presented at a medical meeting in November, Doberstein said.

While Nektar retains full ownership to NKTR-214, it has granted Bristol an open to negotiate for first rights to the drug under the new collaboration.

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.