The tentative agreement on trade negotiated by a dozen Pacific Rim nations will slightly pry open Japan¡¯s famously closed rice market, protect brand-name drugs from generic competitors for at least five years and lower tariffs on automobiles.

The Trans-Pacific Partnership, as the pact is known, will rewrite the rules of commerce among 12 nations that collectively produce an estimated 40 percent of the world¡¯s economic output. It still faces hurdles, such as a vote in the U.S. Congress, but if ratified would have a far-reaching impact on goods and services.

Pharmaceuticals