As an advisory panel for the FDA prepared to take up the matter Tuesday of safety issues with Astrazeneca plc’s marketed dipeptidyl peptidase-4 (DPP-4) inhibitor for diabetes, Viking Therapeutics Inc. lowered the target for its IPO in a move that could help the firm advance the licensing deal with Ligand Pharmaceuticals Inc. – also with a strong diabetes component, though otherwise unrelated and involving drugs with a different mechanism of action).