Bristol-Myers Squibb Company (NYSE:BMY) shares were declining Monday as the company joined forces with another company to develop a cancer drug that’s been disappointing so far.

The pharmaceutical company collaborated in a clinical trial with its cancer drug Opdivo and Nektar Therapeutics’ (NASDAQ:NKTR)  NKTR-214. The result was underwhelming as Wall Street investors were not impressed by the end result.

Analysts said that the phase 1/2 clinical trial data was “underwhelming” and “immature,” sending both stocks dropping early Monday. The effort was designed to create a treatment that combines two cancer drugs, a move that many companies have been making lately to improve patient outcomes.

Opdivo is a popular and effective cancer drug as things stand and the trial was supposed to prove that NKTR-214 enhances the effects of Opdivo when linked up to the drug. The move is especially disappointing considering that Bristol-Myers announced the $1.85 million deal with Nektar on Valentine’s Day and it had great expectations of the combination of these drugs.

The February move was designed to limit Bristol-Myers’ upfront payments and its risk. The deal made Nektar eligible for up to $1.78 billion in milestone payments and allowed for profit sharing geared in Nektar’s favor, which saw Bristol-Myers get a 35% cut of net profits and losses for NKTR-214.

BMY stock fell about 3.3% on Monday as the company’s cancer drug disappointed, while NKTR shares plummeted 43.6% today.