Silicon Valley Bank shares dropped 60 percent in after-hours trading on Thursday after the commercial bank announced a plan to raise more than $2 billion in capital to help offset losses on bond sales. CEO Greg Becker stated in a company letter on Wednesday that the company has sold “substantially all” its available-for-sale securities and was aiming to raise $2.25 billion. The firm is primarily involved with startup companies, and it cited higher interest rates and “elevated cash burn from our clients” as its motive for raising more capital.