This latest acquisition by Pfizer will add four approved cancer therapies to their portfolio, which together generated nearly $2 billion in sales in 2022. Seagen is a pioneer in antibody-drug conjugates, which essentially work like "guided missiles" designed to target and destroy cancer cells while leaving healthy cells unharmed.

CEO Albert Bourla says that this deal will help Pfizer move into an area that is more protected from regulatory and patent issues. It's also a smart move for Seagen, as the Biden administration's Inflation Reduction Act is set to benefit the company's expensive treatments, which will be more accessible to patients with out-of-pocket healthcare spending caps.

Pfizer will pay $229 in cash per Seagen share, a 32.7% premium to Friday's closing price, which sent Seagen's shares soaring to $200 in early trading.

This acquisition comes as Pfizer is preparing for a significant decline in COVID-19 product sales and stiff competition for some of its top-selling drugs. The company expects to generate more than $10 billion in sales from Seagen products alone by 2030, in addition to the $15 billion from its other recent acquisitions.

Pfizer's recent deals include the purchase of Global Blood Therapeutics for $5.4 billion, migraine drug maker Biohaven Pharmaceutical Holding for $11.6 billion, and drug developer Arena Pharmaceuticals for $6.7 billion.

Pfizer's current portfolio of oncology therapies includes 24 approved drugs, while Seagen's includes Adcetris for lymphoma, Padcev for bladder cancers, Tivdak for cervical cancer, and breast cancer treatment Tukysa.

The deal is expected to be completed in late 2023 or early 2024, and while antitrust regulators may closely review it due to its size, Pfizer believes it will eventually be approved.

This is definitely one to watch as Pfizer makes bold moves in the world of cancer treatments and continues to diversify its portfolio beyond COVID-19 products.