HEALTH

Amgen Makes Takeover More Difficult: The Thousand Oaks-based biotechnology company, long the subject of takeover rumors, said it has strengthened its shareholder rights takeover defense. Amgen Inc. insisted, however, that the move wasn’t a response to any buyout effort. Shareholder rights plans are often known as “poison pill” defenses because they make a hostile acquisition prohibitively expensive. Amgen’s plan gives current shareholders the right to buy Amgen stock at half the market price. Amgen’s defense mechanism now would be triggered if any unfriendly suitor acquired 10% of its stock. The previous trip point had been 15%. Amgen said its board reaffirmed that Amgen holders will be best served if the company remains independent.