Strategic Partnership - Alpine entered a strategic partnership with Horizon Therapeutics, receiving a \$25 million upfront payment and a \$15 million equity investment at a 25% premium, with potential milestones totaling \$1.52 billion[6,8] - Alpine also has a strategic partnership with AbbVie for Acazicolcept, including a \$60 million upfront payment and up to \$805 million in potential option exercise and milestone payments[87] Davoceticept (ALPN-202) - Davoceticept is being evaluated in a Phase 1/1b study as monotherapy and in combination with KEYTRUDA® for advanced malignancies[5] - In preclinical studies, Davoceticept demonstrated superior efficacy to PD-L1 inhibition as a monotherapy[25,27] - In a Phase 1 study with 32 subjects, 66% experienced any related adverse event, and 3% experienced a Grade ≥ 3 related adverse event[32,33] - Early clinical data for Davoceticept monotherapy showed a partial response in 4.3% and stable disease in 57% of evaluable patients[38] ALPN-303 - ALPN-303 is a dual B cell cytokine antagonist targeting BAFF and APRIL, with a Phase 1 study in healthy volunteers anticipated in mid-2022[5] - Preclinical data suggests ALPN-303 exhibits superior BAFF/APRIL inhibition compared to existing inhibitors[55] - In non-human primates, ALPN-303 demonstrated increased exposure and enhanced immunoglobulin suppression compared to WT TACI-Fc[62] Acazicolcept (ALPN-101) - Acazicolcept is a dual CD28/ICOS antagonist being developed for autoimmune/inflammatory diseases and is currently in Phase 2 for Systemic Lupus Erythematosus[5,85] - Phase 1 data showed dose-proportional PK/PD and was well-tolerated in humans[83,84]

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37449 ALPINE IMMUNE SCIENCES, INC. (Exact name of registrant as specified in its charter) Delaware 20-8969493 (State or other ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-37449 ALPINE IMMUNE SCIENCES, INC. (Exact name of registrant as specified in its charter) Delaware 20-8969493 (State or other juri ...