Efficacy & Safety Comparison of Epiduo With Doxycycline Versus Vehicle With Isotretinoin in the Treatment of Severe Acne

Inclusion Criteria: 1. Male or female subject of any race, aged 12 to 35 years inclusive 2. Subject weighing between 50 and 110 kg 3. Subject with severe acne (IGA at least 4), which in the opinion of the investigator is appropriate for treatment with oral isotretinoin (severe nodular acne, severe inflammatory acne, recalcitrant acne; all unresponsive to conventional first line therapies) 4. Subject with at least 5 nodules on the face Exclusion Criteria: 1. Subject with clinically abnormal results to blood testings performed at screening 2. Subject with acne conglobata, acne fulminans, secondary acne (chloracne, drug-induced acne, etc.), pyoderma faciale, sinus tracks 3. Female subject who is pregnant, nursing or planning a pregnancy during the study 4. Subject with known history of hepatic and/or renal insufficiency, to be confirmed by blood testings 5. Subject with known metabolic or structural bone disease (for 12-17 years old population) 6. Subject with bowel disease and/or with hypervitaminosis A 7. Subject who presents with treated or untreated depression or has a history of depression including a family history of major depression 8. Subject with a wash-out period from baseline for topical treatment on the face less than : Corticosteroids, antibiotics, antibacterials, antiseptics, retinoids, other anti-inflammatory drugs or other acne treatments (2 weeks); Cosmetic procedures (1 week); Photodynamic therapy and laser therapy for acne (3 months) 9. Subject with a wash-out period from baseline for systemic treatment less than: Corticosteroids, antibiotics (4 weeks),Progesterone for contraception (3 months); Spironolactone(3 months); Other acne treatments (6 months);Cyproterone acetate(6 months)