Changes in the following sections. Medical Monitor / Emergency Contact Information Celgene therapeutic area head signature page Introduction Exclusion Criteria for All Subjects Exclusion Criteria for All Subjects (Section 4.3.1) and Prohibited Concomitant Medications and Procedures Prohibited Concomitant Medications and Procedures Table of Events Sample Size and Power Considerations Discontinuations

• Medical Monitor / Emergency Contact Information ­ Contact information was changed to replace medical monitor’s phone numbers with hotline number • Protocol Summary and Overall Study Design (Section 3) ­ Screening period was extended to 10 weeks to allow enough time for completion of study procedures. • Study Population (Section 4) ­ Inclusion criterion #5 was updated to clarify that the historical liver biopsy in subjects who had been on therapy for treatment of NASH is not to be accepted. ­ Inclusion criteria #6 and #7 were updated to ensure stable doses of medications prior to and after historical liver biopsy is obtained, if the historical biopsy was going to be used for the inclusion criteria. ­ Exclusion criterion #3 was corrected. ­ Exclusion criterion #17 were updated to clarify that positive screening hepatitis B/C is also exclusionary for the study. ­ Exclusion criterion #31 was added to exclude subjects with history of Gilbert's syndrome since clinical manifestations of Gilbert's syndrome might confound the safety and efficacy assessments of CC-90001. • Table of Events (Section 5) and Procedures (Section 6) ­ Added screening α-fetoprotein test to Table of Events and Procedures sections. Protocol Section 4.3.2 Exclusion Criteria for the Subjects with Stage 3 Fibrosis excludes subjects with a screening α-fetoprotein ≥ 200 ng/mL and α-fetoprotein > 20 ng/mL should be discussed with Sponsor to review the evaluation of Hepatocellular Cancer (HCC). ­ Added ultrasound and α-fetoprotein test at Early Termination Visit to ensure HCC surveillance to be done for early terminated subjects with Stage 4 fibrosis. • Prohibited Concomitant Medications and Procedures (Section 8.2) ­ Acetaminophen dose was corrected. • Individual Subject Stopping Criteria (Section 11.1.1) ­ Clarification was made on FOBT stopping criterion.

Protocol Summary, Rationale (Section 1.3), Study objectives and Endpoints (Section 2), Overall Study Design (Section 3), Study Population (Section 4), Method of Treatment Assignment (Section 7.3), Statistical Considerations (Section 9), Appendix B and Appendix C - Expanded study population to allow subjects with NASH and Stage 2 fibrosis in the study and evaluate efficacy and safety of CC-90001 in these subjects. - References to Appendix B and Appendix C were removed from Study population, Table of Events footnote and Procedures sections because they did not apply to Stage 2 fibrosis. Appendix B and Appendix C were removed as well. Study objectives and Endpoints (Section 2) - Added exploratory endpoint for Ishak score and Section 6.6 Efficacy Assessment was updated accordingly - Exploratory endpoints of 2-dimensional magnetic resonance elastography (MRE), 3-dimentional MRE and magnetic resonance imaging-proton density fat fraction (MRI-PDFF) were updated to add absolute change from baseline - Added N-terminal type III collagen propeptide (PRO-C3) to exploratory pharmacodynamic endpoint Added rationale on assessment of severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) serologic status Added SARS-CoV-2 serology to the Table of Events and Section 6.8.1 Biomarkers/Pharmacodynamics - Added exploratory objective and endpoint on SARS-CoV-2 serology - Revised exclusion criterion #13 to clarify that subjects with SARS-CoV-2 infection within 4 weeks of Screening will be excluded and symptoms must have completely resolved - Added exclusion criterion #34 to exclude subjects who have received live attenuated or investigational SARS-CoV-2 vaccine within 3 months prior to the first dose of study treatment. - Changes were made to clarify that fasting is required for certain visits.

 100 mg dose treatment arm was removed - Data from non-clinical and clinical studies suggest that therapeutic doses in humans are likely to be 200 mg and 400 mg once daily (QD). 100 mg QD dose of CC-90001 is likely not as effective a dose in subjects with NASH and liver fibrosis. The subjects who are randomized to the 100 mg dose group prior to implementation of Protocol Amendment 4 will stay on 100 mg QD dose throughout the study. Stage 4 population was removed - The protocol was revised to focus on assessing the efficacy and safety of CC-90001 in subjects with NASH and Stage 2 or Stage 3 liver fibrosis in this study.  Active Treatment/Extension Phase was removed - Active treatment/extension phase was removed to reduce burden for the subjects due to the Coronavirus Disease 2019 (COVID-19) pandemic and to shorten the duration of the study. Subjects who sign informed consent form (ICF) prior to the implementation of Protocol Amendment 4 will have an option to participate active treatment/extension phase.  Exclusion criterion #21 “Subjects has 2 positive fecal occult blood test (FOBT) during Screening, collected at least 4 weeks apart” was removed - Gastrointestinal (GI) toxicity was noted in nonclinical studies. The clinical studies to date have not indicated an increased risk for GI bleeding. Positive FOBT may be caused by different cuases (such as rectal hemmorhage, ulcers, colitis, divertriculosis). The protocol has excluded the subjects with a history of inflammatory bowel disease and the subjects with a history of bleeding peptic ulcer or bleeding diverticular disease within 5 years. Furthermore, the protocol also implemented FOBT at Screening and approximately every 12 weeks during the study and discontinuation criteria for the subject with positive FOBT in the study. With all these in place the occurrence of GI bleeding in the study continues to be well monitored to ensure safety of subjects over the course of the trial.