TRENTON, N.J. — Health-care giant Johnson & Johnson agreed to acquire Scios Inc., one of the oldest U.S. biotech companies, in a $2.4 billion cash-for-stock-deal, the companies announced Monday.

J&J said its purchase of Scios, based in Sunnyvale, Calif., will help strengthen its drug pipeline. Industry analysts have said the deal also would enable New Brunswick-based J&J to block potential competition to an important rheumatoid arthritis drug.

Under terms of the agreement, Scios shareholders will receive $45 for each outstanding Scios share — a 30 percent premium over where the shares traded Thursday, before talks between the two companies were reported. Scios will retain its name and management.

In morning trading Monday, Scios shares rose $1.57, or 3.7 percent, to $43.77 on the Nasdaq stock market, adding to a 22 percent gain Friday when the talks were first reported. J&J shares rose 61 cents, or 1.2 percent, to $52.45 on the New York Stock Exchange.

The transaction, subject to approval by federal regulators and Scios shareholders, is expected to close in the second quarter of 2003. J&J said it will take a one-time charge of about $700 million, or 23 cents per share.

Richard B. Brewer, Scios president and CEO, called the deal a strategic transaction that offers its shareholders an immediate cash return on their investments.

"Johnson & Johnson's financial and management resources will enable us to realize the full potential of Natrecor and bring significant new products to the market," Brewer said in a statement.

Natrecor, Scios' lone drug on the market, was approved in 2001 for acute heart failure and is mainly used in hospitals. Analysts say it could have far more revenue potential with J&J's huge sales force promoting it.

The genetically engineered protein last year had roughly $100 million in sales.

"Natrecor is a truly unique product for a largely underserved and growing market. Scios also brings an advanced research program on kinase inhibitors, which is an exciting new area of research," said Christine Poon, worldwide chairman for J&J's pharmaceuticals group.

Equally important for J&J, industry analysts say, is Scios' program testing a family of potential arthritis compounds, dubbed SCIO-469, two of which are in early human testing.

SCIO-469 could become the first pill available in the class of genetically engineered drugs, which control hormone-like proteins involved in inflammation and progression of rheumatoid arthritis.

If experiments continue to produce good data and the drug gains approval, it could have been a threat to J&J's Remicade — a potential multibillion dollar drug that is injected, limiting its use.

Scios, founded in 1981 as California Biotechnology, has 450 employees, compared with nearly 110,000 at Johnson & Johnson, which has 198 operating companies in 54 countries.

Besides its well-known baby and wound-care products, J&J is a top maker of contraceptives, contact lenses, skin care products and nonprescription painkillers such as Tylenol and Motrin. Its prescription drugs include the heavily advertised Procrit for anemia and pain treatments Ultram and Duragesic.