UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 Title of each class Trading Symbol(s) Name of each exchange on which registered Common Stock, $0.001 par value per share CTKB The Nasdaq Global Select Market Emerging growth company ☒ 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, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the ...