D-PLEX 302: Efficacy and Safety of D-PLEX in the Prevention of Sternal Infection Post Cardiac Surgery

Inclusion Criteria: 1. Subjects scheduled to elective and/or urgent median sternotomy for cardiac surgery, who are preoperative hemodynamically stable. 2. Males and females. 3. Subjects age of 18 and older. 4. Subjects with both Diabetes Mellitus AND BMI≥30 OR Diabetes Mellitus/BMI≥30 AND at least one of the following: * Current/Previous smoking history ≥30 pack year * Chronic Obstructive Pulmonary Disease (COPD) 5. Female of childbearing potential should have a negative serum pregnancy test prior to index procedure. Note: All female of childbearing potential must agree to use a highly effective method of contraception (such as double barrier, oral or parenteral hormonal, intrauterine device and spermicide) consistently and correctly for the duration of the study. 6. Subject is willing and able to provide a signed Informed Consent Form and is willing and able to comply with study's procedures including follow-up visits. Exclusion Criteria: 1. Subjects undergoing partial sternotomy. 2. Subjects with any preoperative active significant infection. 3. Subjects that received oral or IV doxycycline during the last 4 weeks prior to screening. 4. Subjects with sensitivity to doxycycline and/or to tetracycline family of drugs and/or other study drug ingredients. 5. Subjects with known allergies to more than 3 substances. (An allergy questionnaire will be filled during the screening process). 6. Subjects with history of allergic/hypersensitivity reaction to any substance having required hospitalization and/or treatment with intra-venous steroids/epinephrine or in the opinion of the investigator the patient is at high risk of developing severe allergic/hypersensitivity reactions. 7. Subjects with uncontrolled Asthma (GINA III-IV). 8. Subjects with chronic urticaria. 9. Immunocompromised subjects from any reason, at screening. 10. Subjects with renal failure requiring dialysis. 11. Subjects scheduled to major organ transplantation and/or to other significant concomitant surgical procedure. 12. Subjects scheduled for mechanical assist device. 13. Subjects scheduled to be treated with preventive negative pressure devices. 14. Subjects undergone Cerebro-Vascular Accident (CVA)/Transient Ischemic Attack (TIA) within the past 3 months prior to randomization. 15. Subjects that have undergone previously, any cardiac surgery through sternotomy. 16. Subjects with active or previous malignancy in the chest area. 17. Any subject with active malignancy or with malignancy that has not been in complete remission for at least 5 years. Subjects who have had carcinoma in situ of the cervix, squamous cell carcinoma of the skin and basal cell carcinoma of the skin, are eligible. 18. Pregnant or breast-feeding women or women of childbearing age not protected by an effective contraceptive method of birth control (such as double barrier, oral or parenteral hormonal, intrauterine device and spermicide). 19. Subjects enrolled in any intervention study with an investigational medicinal product and/or received any investigational medicinal product within 30 days or 5½ half-lives of the product prior to enrollment (whichever is longer). 20. In the opinion of investigator, subject is not eligible to participate in the study and/or to comply with protocol requirements (e.g. due to a cognitive, medical condition or residency distanced from site that may jeopardize Follow-Up visits attendance etc.).