Amgen Inc. on Wednesday announced it had been notified of an unsolicited “mini-tender” offer by Canadian investment company TRC Capital Corp. to purchase 500,000 of its shares. A mini-tender offer, according to the Securities and Exchange Commission, is an offer to buy less than 5 percent of another company’s outstanding shares, thereby avoiding many SEC reporting requirements. For Amgen, 500,000 shares would represent way less than 1 percent of its nearly 600 million shares outstanding. According to a statement from the Thousand Oaks biotech, TRC is offering to buy each share for $192, or 4.4 percent below the $200.80 closing price on Oct. 11, when TRC made the offer. In its statement, Amgen said the SEC has cautioned investors about mini-tender offers. The SEC, according to Amgen, noted that these offers “have been increasingly used to catch investors off guard” because they may surrender their stock “assuming that the price offered includes the premium usually present in larger, traditional tender offers.” Amgen recommends against shareholders tendering shares. Shares of Amgen (AMGN) closed Tuesday down $1.51, or less than 1 percent, to $203.32 on the Nasdaq.