SecuritiesRegisteredPursuant TitleofEachClass Stock,$0.001ParValue UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-K ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2019 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: 001-35005 ASSEMBLY BIOSCIENCES, INC. (Exact name of registra ...