The Securities and Exchange Commission approved applications by Seemala Partners L. P. and IFB Managing Partnership L. P. to pay off $640 million in debt and shut down. IFB is a shell with no significant assets, the SEC said. But Seemala was a major trading entity and is the target of millions of dollars in lawsuits resulting from insider trading cases against arbitrageur Ivan F. Boesky. Seemala asked the SEC for permission to withdraw and to repay $640 million in subordinated debt, most of it at a reduced 9% interest rate. The noteholders, in return for payment of the principle, would waive their rights to collect more than $100 million in prepayment penalties and additional interest.