UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q For the quarterly period ended December 31, 2018 x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 OR ¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission File Number: 814-00646 APOLLO INVESTMENT CORPORATION (Exact name of Registrant as specified in its charter) (State or other jurisdiction of incorporation or organization) (I.R.S. Employe ...