Biotechs Rally After Biogen Drug Approval Stokes Optimism (2)

The approval of Biogen Inc.’s new Alzheimer’s disease treatment spurred broad gains in the sector, driving the Nasdaq Biotech Index to surge by the most in seven months.

Shares of Eli Lilly & Co. jumped 10% and closed at a record high, while Biogen’s partner in Japan, Eisai Co., surged 56% in U.S. trading, the biggest gain ever for the stock. Small-cap companies working on treatments for the disease also climbed: Cassava Sciences Inc. rose 5.4%, while Annovis Bio Inc. gained 7.4%.

The Nasdaq Biotech Index rallied 3.6% in New York, the biggest jump since Nov. 4, as Biogen ...