UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 10-Q (Mark One) ☒ 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 For the transition period from to . Commission File Number 001-36510 ZAFGEN, INC. (Exact name of registrant as specified in its charter) Delaware 20-3857670 (State or other jurisdiction of incorporation or organization) (IRS Employer I ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2018 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 001-36510 ZAFGEN, INC. (Exact name of registrant as specified in its charter) (State or other jurisdiction of incorporation or organiza ...

ZGN-1061 for Type 2 Diabetes and NASH - ZGN-1061 Phase 2 proof-of-concept trial demonstrated statistically significant A1C lowering efficacy and weight loss, with a safety and tolerability profile generally comparable to placebo[3] - In the proof-of-concept trial, the 1.8 mg dose of ZGN-1061 showed a statistically significant improvement in A1C compared to placebo (p<0.0001)[6, 7] - The 1.8 mg dose of ZGN-1061 also showed a statistically significant improvement in weight compared to placebo (p<0.0001)[8] - Nonclinical studies of ZGN-1061 have demonstrated significant NASH model efficacy, and complementary efficacy in combination with a GLP-1[3] - Plasma ALT decreased by 25% and 44% in 0.06 mg/kg and 0.3 mg/kg ZGN-1061 groups respectively in NASH nonclinical study[10] ZGN-1258 for Prader-Willi Syndrome - Development plans for ZGN-1258 were suspended due to an unexpected finding in long-term toxicology studies[4] - Prader-Willi syndrome affects approximately 200,000 patients worldwide[18] - Over 400 participants enrolled in PATH for PWS natural history study as of March 2019[20] ZGN-1345 for Metabolic Liver Disease - ZGN-1345 was named as a development candidate in 4Q 2018[4] - ZGN-1345 is an orally dosed MetAP2i with high liver concentrations but minimal-to-no detectable systemic exposure; once daily dosing expected[4, 21] Financial Status - As of December 31, 2018, the company had a cash position of $118 million, expected to extend through at least 2020[4] Type 2 Diabetes Market - There are 415 million people worldwide living with type 2 diabetes, expected to grow to 642 million by 2040[5] - Over 50% of patients with type 2 diabetes have uncontrolled A1C, despite multiple approved treatments available[5]

Zafgen, Inc. (ZFGN) Q4 2018 Earnings Conference Call March 11, 2019 4:30 PM ET Company Participants John Woolford - IR, Westwicke Partners Jeffrey Hatfield - CEO Patricia Allen - CFO Conference Call Participants Ted Tenthoff - Piper Jaffray Operator Good day, ladies and gentlemen, and welcome to Zafgen's Fourth Quarter and Full Year 2018 Financial Results and Update Conference Call. At this time, all participants are in a listen-only mode. Later, we will conduct a question-and-answer session and instruction ...