Arena Pharmaceuticals Inc. ARNA, +28.68% ticked lower Tuesday after the biotech company announced a secondary offering of shares. Arena shares declined 1.9% after hours, following a surge of 29% to close the regular session at $39.75 on positive clinical results for an ulcerative colitis treatment study. Arena said it will offer 7.5 million shares, with an option to underwriters for 1.1 million more to cover overallotments. Arena has about 39.2 million shares outstanding.