The stock market moved higher again on Monday morning, building on gains from Friday. Good news from Pfizer (PFE 0.11%) was encouraging to the broader market, as it inspired investors to believe they might be one step closer to the end of the COVID-19 pandemic. As of 11 a.m. EDT, the Dow Jones Industrial Average (^DJI 0.23%) was up 253 points to 35,373. The S&P 500 (^GSPC 0.80%) gained 39 points to 4,480, and the Nasdaq Composite (^IXIC 1.14%) picked up 187 points to 14,902.

Pfizer's stock was among the best performers in the Dow on a percentage basis thanks to a couple of news items that lifted its share price. Nevertheless, Pfizer's gains were minimal compared to the boosts in the other companies involved with the drugmaker. Below, we'll look at what good news for Pfizer meant for BioNTech (BNTX 2.23%) and Trillium Therapeutics (TRIL).

Full approval for the Pfizer/BioNTech vaccine

Pfizer's big news was that the U.S. Food and Drug Administration fully approved the COVID-19 vaccine it developed with BioNTech. Shares of BioNTech surged higher by more than 10% on Monday morning in the wake of the news.

Medical professional administering an injection to a patient.

Image source: Getty Images.

The Pfizer/BioNTech vaccine had already been extremely popular both in the U.S. and worldwide as one of the most effective COVID-19 vaccines on the market. However, the companies had been delivering inoculations under an Emergency Use Authorization from the FDA, which created some limitations on its use and the manner in which the companies marketed and priced the vaccine.

The FDA almost seemed more excited about the development than Pfizer and BioNTech. The regulatory agency's press release heralded the approval as a key milestone against COVID-19, arguing that the public should be even more confident about "high standards for safety, effectiveness, and manufacturing quality" because of the approval.

BioNTech has played second fiddle to rival Moderna (MRNA 3.06%) among vaccine stocks. However, being first to full FDA approval is a distinction that could help bolster BioNTech's long-term prospects.

Trillium gets an offer no one could refuse

Meanwhile, shares of Trillium Therapeutics skyrocketed 188%. The cancer specialist got a buyout bid from Pfizer at a premium that few acquisitions command, even in the highly lucrative biotech and pharma field.

Pfizer agreed to pay a total of $2.26 billion for Trillium. Trillium's shareholders will receive $18.50 per share in cash. Given that the stock closed at just over $6 per share on Friday afternoon, it's clear that Pfizer was willing to pay up, calculating its offer at a 118% premium to the weighted average share price over the past 60 days.

Pfizer is optimistic that Trillium will help bolster its oncology and hematology portfolio of pipeline treatments, with an emphasis on patients suffering from blood-related cancer. Trillium's clinical-stage candidates are unique in the way they fight cancer, with the potential to change the way medical professionals treat patients with the disease.

Buying early stage biotechs is always risky, but given Trillium's potential, Pfizer investors seem happy about the acquisition. Only time will tell, though, whether the move ends up working to Pfizer's advantage in the long run.