Carlsbad-based Isis Pharmaceuticals, a firm developing antisense drugs for treating cardiovascular, metabolic and severe neurodegenerative diseases, and cancer, said this morning it has earned $6M in a milestone payment from Bristol-Myers Squibb Company. The firm said the payment came due to acceptance of initial regulatory filings to begin Phase I clinical studies for a drug targeted at lowering LDL cholesterol. The firm's BMS-PCSK9Rx drug is a collaboration between Isis and Bristol-Myers Squibb.