What happened

Seattle Genetics (NASDAQ:SGEN) shares rose 48.7% in the first half, according to data provided by S&P Global Market Intelligence, after the company gained U.S. regulatory approval for its second drug in less than six months.

Two researchers look into a microscope in a lab.

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The U.S. Food and Drug Administration in April approved Tukysa for patients with metastatic HER2-positive breast cancer after approving Padcev in December for locally advanced or metastatic urothelial cancer. In Padcev's first full quarter of commercialization, the drug generated $34.5 million in net sales, the company reported.

So what

Urothelial cancer is the most common form of bladder cancer, and according to Grand View Research, the global drug market for the disease is growing at a 22.9% compound annual growth rate and is set to reach $3.6 billion by 2023. The global HER2-positive breast cancer market, at a 4.4% compound annual growth rate, may reach nearly $10 billion by 2025, a Global Data report shows. With these growing markets, Tukysa and Padcev have plenty of room to deliver sales increases.

Seattle Genetics' drug Adcetris, for Hodgkin lymphoma, was approved in 2011. Adcetris sales climbed 22% in the first quarter, and the company forecasts more growth as it works to further establish the drug as part of a frontline treatment, or first treatment given to patients.

Now what

The European Medicines Agency is currently reviewing Tukysa, so investors will be watching for a possible approval in Europe. Sales figures from Padcev's second quarter on the market will be another factor that could offer the stock direction in the second half of the year.

In more positive news, Seattle Genetics recently reported encouraging data from its phase 2 trial of tisotumab vedotin for recurrent or metastatic cervical cancer. The biotech company plans to speak with the FDA about the possibility of an accelerated approval process for the drug candidate. If the FDA agrees to an accelerated pathway, that likely will be another positive driver for Seattle Genetics' shares.

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