Positive top-line efficacy data for migraine prevention drug ALD403 pushed Alder Biopharmaceuticals Inc. shares (NASDAQ:ALDR) 50 percent higher to $25.70 by Monday market close, bolstering the company's standing in a race to bring the first calcitonin gene-related peptide (CGRP) receptor antagonist to what's expected to be a multibillion-dollar market.