1. Omadacycline in Acute Skin and Skin Structure Infections Study (OASIS) A Phase 3 Randomized, Double-Blind, Multi-Center Study to Compare the Safety and Efficacy of Oral and IV Omadacycline to Linezolid for Treating Adult Subjects with ABSSSI 16 June 2016 ABSI-1108 Study Design: Top-Line Data Results 1

2. This presentation contains “forward-looking” statements that are within the meaning of federal securities laws and are based on our management’s beliefs and assumptions and on information currently available to management. Forward- looking statements include information concerning our possible or assumed future results of operations, business strategies, financing plans, competitive position, industry environment, potential growth opportunities, potential market opportunities and the effects of competition. Forward-looking statements include all statements that are not historical facts and can be identified by terms such as “anticipates,” “believes,” “could,” “seeks,” “estimates,” “intends,” “may,” “plans,” “potential,” “predicts,” “projects,” “should,” “will,” “would” or similar expressions and the negatives of those terms. Forward-looking statements represent our management’s beliefs and assumptions only as of the date of this presentation. Our operations involve risks and uncertainties, many of which are outside our control, and any one of which, or combination of which, could materially affect our results of operations and whether the forward-looking statements ultimately prove to be correct. Factors that may materially affect our results of operations include, among other things, those listed in our Annual Report on Form 10-K and other filings with the Securities and Exchange Commission (“SEC”). Except as required by law, we assume no obligation to update these forward-looking statements publicly, or to update the reasons actual results could differ materially from those anticipated in the forward-looking statements, even if new information becomes available in the future. You may get copies of our Annual Report on Form 10-K, Quarterly Report on Form 10-Q and our other SEC filings for free by visiting EDGAR on the SEC website at http://www.sec.gov. Safe Harbor Statement

3. Omadacycline SPA-Approved Phase 3 Trial Design for ABSI -1108 (OASIS) [1] 655 Randomized Subjects, 10 subjects were randomized, but never treated [2] Early Clinical Response = primary end point for FDA. [3] PTE end point = Co-primary end points confirmed through EMA scientific advice. d2-3 FDA - Early Clinical Response [2] d7 to d14 End of Treatment d1 Omadacycline IV Omadacycline IV or Oral Linezolid IV Linezolid IV or Oral ABSSSI 645 treated subjects [1] 7-14d after last treatment day EMA - Post-Treatment Evaluation [3] 3

4. Key Populations: –Safety population  Subjects who received test article –Modified Intent-to-treat (mITT) population  Randomized subjects without a sole Gram-negative causative pathogen –Clinically evaluable (CE) population  mITT subjects who had a qualifying ABSSSI, PTE assessment, and met other key evaluability criteria (e.g., had no potentially confounding antibacterial therapy or surgical procedures) Key Populations 4

5. Demographics and Baseline Characteristics 5

6. Key Populations ITT: all subjects who were randomized Safety: subjects who received test article mITT: randomized subjects without a sole Gram-negative causative pathogen at Screening CE-PTE:mITT subjects who received test article, had a qualifying ABSSSI, an assessment of outcome at PTE, and met other key evaluability criteria (e.g., had no potentially confounding antibacterial therapy or surgical procedures) 6

7. Safety Population Demographics 7

8. Primary ABSSSI Infection Type at Baseline (mITT Population) 8

9. Clinical Efficacy Results 9

10. Primary Endpoints Achieved for Both FDA and EMA EMA Co-Primary Endpoints Delta (95% CI) -0.7 (-6.9, 4.9) Delta (95% CI) +2.5 (-3.2, 8.2) Delta (95% CI) +2.8 (-1.0, 6.9) 10 FDA Primary Endpoint

11. Safety Results 11

12. Premature Discontinuation – Safety Population 12

13. Overview of Adverse Events – Safety Population 1 TEAE is defined as an AE occurring after first dose of active test article. 13

14. Most Frequent TEAEs (> 3%) – Safety Population 1 Nausea: Omadacycline = 87.5% mild,12.5% moderate; Linezolid = 78.1% mild, 21.9% moderate 2 Events were reported as IV site infiltration, typically due to difficulty in finding reliable venous access sites. All events were mild. All but 3 subjects (2 omadacycline and 1 linezolid) had a history of drug abuse. Among these subjects, 79% in each treatment group had ABSSSI considered related to intravenous drug use. 14

15. Infusion Site Reactions – Safety Population 1 Events were reported as IV site infiltration, typically due to difficulty in finding reliable venous access sites. All events were mild. All but 3 subjects (2 omadacycline and 1 linezolid) had a history of drug abuse. Among these subjects, 79% in each treatment group had ABSSSI considered related to intravenous drug use. 2 MedDRA preferred terms = infusion site pain, infusion site erythema, infusion site irritation, infusion site discomfort, infusion site inflammation, and infusion site swelling. 15

16. Liver Chemistry – Safety Population No subjects met laboratory criteria for Hy’s Law 16