X0306 4 2019-06-13 0 0001080709 ARENA PHARMACEUTICALS INC ARNA 0001650322 Dallas Jayson Donald Alexander C/O ARENA PHARMACEUTICALS, INC. 6154 NANCY RIDGE DRIVE SAN DIEGO CA 92121 1 0 0 0 Common Stock 2019-06-13 4 A 0 2654 0.00 A 5704 D Common Stock 2019-06-14 4 S 0 1355 55.8184 D 4349 D Common Stock 2019-06-14 4 S 0 170 56.5082 D 4179 D Stock Option (right to buy) 56.50 2019-06-13 4 A 0 5000 0.00 A 2026-06-13 Common Stock 5000 5000 D The amount represents restricted stock units that vest in full on the earliest of June 13, 2020, or the date of Arena's next annual meeting of stockholders. The shares underlying the restricted stock units will be issued upon vesting of the restricted stock units. The sale reported in this Form 4 was effected pursuant to a Rule 10b5-1 trading plan established by the reporting person. The price reported in column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $55.42 to $56.27, inclusive. The reporting person undertakes to provide Arena Pharmaceuticals, Inc., any security holder of Arena Pharmaceuticals, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes 3 and 4 to this Form 4. The price reported in column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $56.48 to $56.64, inclusive. The options vest in 12 equal monthly installments (except as otherwise necessary to avoid vesting of a fractional share) over one year beginning on July 13, 2019, and are exercisable once vested. /s/ Veronica Vallejo, as Attorney-in-Fact 2019-06-17