A Phase 2a Randomized, Double-Blind, Placebo-Controlled Study to Characterize the Pharmacokinetics and Pharmacodynamics of Rifaximin Novel Formulations in Patients With Sickle Cell Disease
Phase: PHASE2
Conditions: Sickle Cell Disease
Sponsor: Bausch Health Americas, Inc.

Protocol RBSC2161; Version 6.0, 12 April 2022 
Salix Pharmaceuticals, Inc 
CONFIDENTIAL 
 Page 1 of 77 
TITLE PAGE 
CLINICAL RESEARCH PROTOCOL 
A Phase 2a Randomized, Double-Blind, Placebo-Controlled Study to 
Characterize the Pharmacokinetics and Pharmacodynamics of Rifaximin 
Novel Formulations in Patients with Sickle Cell Disease  
Protocol ID: 
RBSC2161 
IND Number: 
150048 
Clinical Phase: 
2a 
Treatment Regimen: Rifaximin Extended Release (ER) or Delayed Extended Release (DER) 
40 or 80 mg or Placebo BID for 4 weeks 
Sponsor: 
Salix Pharmaceuticals, Inc. a division of Bausch Health US, LLC 
400 Somerset Corporate Blvd. 
Bridgewater, NJ, USA 08807 
Main Office: +1.908.927.1400 
Medical Monitor: 
Principal 
Investigator: 
Multicenter 
Protocol Date: 
12 April 2022, Version 6.0 (Amendment 5) 
30 March 2022, Version 5.0 (Amendment 4) 
12 January 2022, Version 4.0 (Amendment 3) 
22 November, 2021Version 3.0 (Amendment 2) 
16 AUGUST 2021, Version 2.0 (Amendment 1) 
06 MAY 2021, Version 1.0 (Original) 
NCT05098028

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 2 of 77 
 
This protocol contains confidential information about a product provided by Salix Pharmaceuticals, Inc. a 
division of Bausch Health US, LLC.  This information is provided for the exclusive use of the Investigators 
participating in this study.  Any and all confidential information contained herein may not be disclosed to any 
other person or party without the prior written consent of Salix Pharmaceuticals, Inc. or Bausch Health 
Companies Inc, and its affiliates including but not limited to Bausch Health US, LLC and Bausch Health 
Americas, Inc. 

CONFIDENTIAL 
 Page 3 of 77 
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 4 of 77 
 
INVESTIGATOR PROTOCOL AGREEMENT 
I agree: 
• To assume responsibility for the proper conduct of the study at this site. 
• To conduct the study in compliance with this protocol, with any future amendments, and with 
any other study conduct procedures provided by the Sponsor, Salix Pharmaceuticals, Inc. a 
division of Bausch Health US, LLC (Salix). 
• Not to implement any deviations from or changes to the protocol without agreement from the 
Sponsor and prior review and written approval from the Institutional Review Board/Ethics 
Committee (IRB/EC), except where necessary to eliminate an immediate hazard to the 
subjects, or for administrative aspects of the study (where permitted by all applicable 
regulatory requirements). 
• That I am thoroughly familiar with the appropriate use of the investigational drug(s), as 
described in this protocol and any other information provided by the Sponsor including, but 
not limited to the following: the current Investigator’s Brochure or equivalent document 
provided by Salix, and the approved product label, if applicable. 
• That I am aware of, and will comply with, “good clinical practices” (GCP) and all applicable 
regulatory requirements. 
• To ensure that all persons assisting me with the study are adequately informed about the 
investigational drug(s) and of their study-related duties and functions as described in the 
protocol. 
• To periodic on-site monitoring of the electronic case report forms (eCRFs) and source 
documents by Salix or designee and to on-site inspection of eCRFs and source documents by 
appropriate regulatory authorities, including but not limited to, the US Food and Drug 
Administration (FDA), local governing regulatory bodies, and IRB/EC inspectors. 
• That I have been informed that certain regulatory authorities require the Sponsor to obtain and 
supply details about the Investigator’s ownership interest in the Sponsor or study drug, and 
more generally about his/her financial ties with the Sponsor.  Salix will use and disclose the 
information solely for the purpose of complying with regulatory requirements. 
Hence, I: 
– Agree to supply Salix with any information regarding ownership interest and financial ties 
(including those of my spouse and dependent children); 
– Agree to promptly update this information if any relevant changes occur during the course 
of the study and for 1 year following completion of the study; and 
– Agree that Salix may disclose this information about such ownership interests and financial 
ties to regulatory authorities. 
 
 
 
 
 
 
Investigator Name [Print]  
Investigator Signature 
 
Date 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 5 of 77 
 
SYNOPSIS 
PROTOCOL TITLE 
A Phase 2a Randomized, Double-Blind, Placebo-Controlled Study 
to Characterize the Pharmacokinetics and Pharmacodynamics of 
Rifaximin Novel Formulations in Patients with Sickle Cell 
Disease 
PROTOCOL NUMBER 
RBSC2161 
SPONSOR 
Salix Pharmaceuticals, Inc., a division of Bausch Health US, LLC 
INVESTIGATIONAL 
PRODUCT 
Rifaximin Extended Release (ER) 20 mg Capsules, Delayed 
Extended Release (DER) 20 mg Capsules, and placebo capsules 
OBJECTIVES 
The objectives of this study are: 
• 
To characterize the pharmacokinetics/pharmacodynamics 
(PK/PD) of rifaximin ER and DER in subjects with sickle 
cell disease (SCD)  
• 
To assess the safety and tolerability of rifaximin ER and 
DER  
TREATMENT 
Subjects will be enrolled and randomized 2:2:1:2:2:1 to one of 6 
parallel arms to receive oral treatment twice daily (BID) for 
approximately 29 days: 
• 
Group 1: 40 mg rifaximin ER, BID  
• 
Group 2: 40 mg rifaximin DER, BID 
• 
Group 3: Placebo for 40 mg rifaximin, BID 
• 
Group 4: 80 mg rifaximin ER, BID  
• 
Group 5: 80 mg rifaximin DER, BID 
• 
Group 6: Placebo for 80 mg rifaximin, BID 
STUDY DESIGN 
This is a randomized, double-blind, placebo-controlled study in 
SCD subjects with a history of Vaso-occlusive Crises (VOCs).  
Approximately 60 subjects with SCD will be enrolled and 
randomized: 12 subjects in each of four active rifaximin groups 
and 6 subjects in each of 2 placebo groups.  
After a Screening period of up to 21 days, eligible subjects will 
visit the study site on Day 1. After all Baseline assessments (Day 
1 pre-dose) are completed, the study staff will administer subjects 
their AM dose of assigned treatment. The subject will remain at 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 6 of 77 
 
the study site for 8 hours after dosing and safety parameters and 
samples for PK (rifaximin and 25-desacetyl rifaximin) will be 
collected for 8 hours post-dose. After completing all 8-hour 
assessments, and the safety parameters are acceptable to the 
Investigator, the subjects can go home. Subjects will administer 
their Day 1 PM dose at home.  
Subjects will return to the study site for outpatient visits on Days 
8, 15, and 29 (±1 day each) for pre-dose PK, PD, and safety 
assessments.  
At the final visit (Day 29 [±1 day]), subjects will administer only 
the AM dose of treatment. Subjects will remain at the clinical site 
through 8 hours post-dose for collection of PK samples.  Subjects 
will return to the site on the following days for post-final dose PK 
assessments as follows: 
Day 30:  
• 
24 hours post-dose 
• 
30-hours post-dose  
Day 31: 48 hours post-dose 
Day 32: 72 hours post- dose 
Two weeks after the last dose subjects will return to the study site 
for a final follow-up visit on Day 43 (±3 days). Subjects will be 
discharged from the study after completing all assessments on the 
Day 43 visit. 
At every study visit, subjects will also report opioid use since their 
previous visit.  Site staff will record opioid use. 
Safety, tolerability, PK, and PD data will be collected during each 
visit at the timepoints listed in the Schedule of Assessments. 
STUDY DURATION 
Subject participation will be up to 9 weeks, including a Screening 
Period of up to 21-days, a 4-week Treatment Period, and 2-week 
Follow-up. 
SUBJECT POPULATION 
Male and non-pregnant, non-nursing females ≥18 and ≤70 years 
with SCD and at least 2 VOCs in the previous 12 months. 
NUMBER OF SUBJECTS 
Up to 60; 12 subjects in each of 4 active rifaximin groups and 6 
subjects in each of 2 placebo groups. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 7 of 77 
 
NUMBER OF CENTERS 
Approximately 20 
LOCATION 
Multicenter study in North America, Middle East, and Africa 
CRITERIA FOR INCLUSION 
A subject will be eligible for inclusion in this study if he/she 
meets all the following criteria: 
1. Subject must have the ability and willingness to sign a 
written informed consent form. 
2. Subject is between the ages of 18 to 70 years old (inclusive) 
at the time of consent. 
3. Subject has SCD of any genotype (HbSS, HbSC, HbS β-
thalassemia).  If the subject’s genotype has not been 
previously documented, genotyping will be performed 
during Screening using high-performance liquid 
chromatography (HPLC)/electrophoresis. 
4. Subject must have experienced at least 2 VOCs within the 
12 months prior to Screening. A VOC is defined as: 
a. The occurrence of appropriate symptoms consistent 
with a painful crisis, acute chest syndrome (ACS), or 
priapism (Section 2.2.3)  , and  
b. Requires a visit to a medical facility and/or 
healthcare professional, and  
c. Receipt of either a parenteral or oral opioid or 
NSAID analgesia.  
5. If subject is receiving hydroxyurea (HU)/hydroxycarbamide 
(HC), subject must have been receiving the treatment for at 
least 6 months prior to Screening and must agree to 
maintain the same dose and schedule for the duration of the 
study.  
6. Subjects must have laboratory values at Screening as 
follows: 
a. Absolute Neutrophil Count (ANC) ≥1.0 x 109/L 
b. Platelets ≥ 75 x 109/L 
c. Hemoglobin (Hgb) ≥ 6.0 g/dL 
d. Glomerular filtration rate (GFR) ≥ 45 mL/min/1.73 
m2 using the CKD-EPI formula 
e. Total bilirubin ≤ 15 mg/dL 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 8 of 77 
 
f. Alanine transaminase (ALT) ≤ 3.0 x ULN 
g. International Normalized Ratio (INR) ≤ 2.0 
7. Eastern Cooperate Oncology Group (ECOG) performance 
status ≤ 2 
8. Women of child-bearing potential, defined as all women 
physiologically capable of becoming pregnant, must have a 
negative serum pregnancy test at Screening and agree to use 
standard prevention methods for the duration of the study. 
CRITERIA FOR EXCLUSION 
A subject will not be eligible for inclusion in this study if any of 
the following criteria apply: 
1. Subject is receiving concomitant treatment with voxelotor, 
crizanlizumab, or L-glutamine. 
2. Subject has any history of stem cell transplant, is planning 
to begin or has received in past 30 days. 
3. Subject experiences an acute VOC, requiring a visit to a 
medical facility and/or healthcare professional, ending 
within 7 days prior to Day 1 dosing. 
4. Subject has received any blood products within 30 days 
prior to Day 1 dosing. 
5. Subject has uncontrolled liver disease or renal impairment, 
ulcerative colitis, Crohn’s disease, or other chronic GI 
disorder. 
6. Subject has received active treatment in another 
investigational trial within 30 days or 5 half-lives of the last 
dose of the investigational agent, whichever is greater, prior 
to Screening. 
7. Subject has received penicillin prophylaxis or antibiotics for 
treatment of infection within 30 days or 5 half-lives of the 
treatment, whichever is greater, prior to Screening. 
8. Subject has a significant medical condition that required 
hospitalization (other than for a VOC) within 2 months 
prior to Screening. 
9. Subject is planning on undergoing an exchange transfusion 
during the duration of the study or has completed one 
within 4 weeks prior to Day 1 dosing. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 9 of 77 
 
10. Subject has a hypersensitivity to rifaximin, rifampin, 
rifamycin antimicrobial agents, or any components of 
rifaximin ER and DER. 
11. Subject is pregnant or a nursing woman. 
12. Subject has a history of illicit drug use or abuse, either 
documented or in the opinion of the Investigator. 
13. Subject is using any medication that is known to inhibit or 
induce CYP3A4, P-gp and OATP1B1/B3 within 30 days or 
5 half-lives, whichever is longer, prior to Day 1 dosing, or 
in the opinion of the Investigator, may affect the evaluation 
of the study product or place the subject at undue risk. 
14. Subject has had any prior gastrointestinal surgery which has 
altered the anatomy of the esophagus, stomach, or 
small/large intestine (with the exception of appendectomy, 
cholecystectomy, and fundoplication). 
15. Subject has had a colonoscopy or sigmoidoscopy within 30 
days prior to Day 1 or plans to undergo such a procedure 
during the duration of the study. 
16. Subject has used bowel prep, laxative, or enema within 30 
days prior to Day 1. 
17. Subject has a bleeding disorder including, but not limited 
to, acquired or congenital platelet function defects, 
disseminated intravascular coagulation (DIC), bleeding 
factor deficiencies, hemophilia, idiopathic 
thrombocytopenia purpura (ITP), or von Willebrand’s 
disease. 
18. Subject is planning to undergo a major surgical procedure 
during the duration of the study. 
19. Subject has a positive test for human immunodeficiency 
virus (HIV)1 or HIV2. 
20. Subject has an active Hepatitis B infection (HBsAg 
positive).  Prior infection that is not active (i.e., HBsAg 
negative, HBcAb positive, and HBsAb positive) is 
permitted.  
21. Subject has a positive test for Hepatitis C (HCV RNA).  
Prior infection with spontaneous resolution or sustained 
resolution for ≥ 24 weeks after cessation of antivirals is 
permitted. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 10 of 77 
 
22. Subject has an active COVID-19 infection or 
complication(s) related to COVID-19 infection that are 
unresolved or, in the opinion of the Investigator, may affect 
evaluation of the study drug or place the subject at undue 
risk. 
23. Subjects has received a vaccine (including COVID-19 
vaccine) within 2 weeks prior to Screening.  If subject has 
received their first of two COVID-19 vaccination doses, as 
applicable, they must wait for at least 2 weeks after receiving 
the second dose, and be symptom-free, prior to beginning 
Screening.  Subject must not be planning for COVID-19 or 
other vaccinations while on study.   
24. Subject has a malignant disease.  Exceptions include 
malignancies that were treated curatively and have not 
recurred within 2 years prior to study treatment, completely 
resected basal cell and squamous cell skin cancers, and any 
completely resected carcinoma in situ. 
25. Subjects has prolonged QT interval as assessed by ECG 
history within the past 3 months.  For subjects with no 
historical ECG information, subject has a resting 
QTcF ≥ 460 msec for males and ≥ 470 msec for females at 
Screening. 
26. Subject has any unstable cardiac condition that, in the 
opinion of the Investigator, may worsen during the study or 
interfere with successful evaluation of the study treatment.  
27. Subject has a serious mental or physical illness which, in 
the opinion of the Investigator, would compromise 
participation in the study. 
28. Subject has any condition which, in the opinion of the 
Investigator, is likely to interfere with the successful 
collection of the measurements required for the study. 
29. Subject is unable to understand or comply with study 
instructions and requirements. 
CRITERIA FOR 
EVALUATION 
Pharmacokinetics and Pharmacodynamics: 
Full rifaximin and 25-desacetyl rifaximin  PK profiles following 
administration on Days 1 and 29 and truncated profiles on Days 8 
and 15 will be evaluated.  

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 11 of 77 
 
Blood samples for PK analysis will be collected at the following 
timepoints: 
• 
Day 1: pre-dose, 0.5, 1, 1.5, 2, 3, 4, 5, and 8-hours post-dose  
• 
Day 8 and Day 15: pre-dose and 0.5, 1, and 2-hours post-dose. 
• 
Day 29: pre-dose, 0.5, 1, 1.5, 2, 3, 4, 5, and 8-hours post-final 
dose. 
• 
Day 30: 24 and 30 hours post-final dose 
• 
Day 31: 48 hours post-final dose 
• 
Day 32: 72 hours post-final dose 
• 
During medical facility visit for VOC with estimated time of 
last dose, when possible.  
PD biomarkers (absolute neutrophil count [ANC], circulating aged 
neutrophils [CANs], serum CD62L, high sensitivity C-reactive 
protein [hsCRP], the gut permeability biomarkers intestinal fatty-
acid binding protein [iFABP], lipopolysaccharide [LPS], and the 
gut bacteria biomarker urine 3-indoxyl sulfate [3-IS Urine]) will 
be collected at the following timepoints: 
• 
Day 1: pre-dose 
• 
Day 8, Day 15, and Day 29: during each visit – pre dose  
• 
Day 31 
• 
Day 43 
• 
During medical facility visit for VOC, when possible. 
Safety:  
Safety will be assessed throughout the duration of the study by 
collection of adverse events (AEs), vital signs (systolic and 
diastolic blood pressure, heart rate, oral body temperature, and 
oxygen saturation), clinical safety laboratory tests (hematology, 
chemistry, urinalysis, and C-reactive protein), physical exams 
(PEs), and electrocardiograms (ECGs).   
Exploratory Assessments: 
At every study visit, subjects will report, and the site staff will 
record, opioid use since their previous visit.   
Information on any potential VOCs experienced during the study 
will be collected as follows: 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 12 of 77 
 
• 
Dates and duration of each episode. A VOC is defined as: 
o The occurrence of appropriate symptoms consistent 
with a painful crisis, acute chest syndrome (ACS), or 
priapism, and  
o Requires visit to a medical facility, and 
o Receipt of either a parenteral or oral opioid or 
NSAID analgesia. 
• 
Categorization of VOCs. Subcategories are uncomplicated 
pain crises, acute chest syndrome (ACS), hepatic 
sequestration, splenic sequestration, and priapism (requiring 
healthcare visit).  
• 
Intravenous opioid analgesia (IOA) and oral opioid use during 
VOCs, including date/time of each start and stop of treatment, 
dose, drug, inpatient/outpatient setting, and date/time of 
readiness-to-discharge. 
SAMPLE SIZE 
The total of 60 subjects is not based on formal statistical 
considerations. Twelve (12) subjects per arm receiving active 
rifaximin is considered adequate to evaluate the PK/PD of 
rifaximin ER and DER. 
STATISTICAL 
METHODOLOGY 
Pharmacokinetics and Pharmacodynamics: 
PK will be evaluated by noncompartmental analysis following the 
first dose on Day 1 and the final dose on Day 29. Steady state will 
be assessed for all subjects based on Ctrough on Day 8, Day 15, and 
Day 29.  
Following the first dose on Day 1, Cmax, Tmax, AUC0-8h,  AUClast, 
and MR_AUC0-8h will be estimated. 
Following the final dose on Day 29, Cmax, Tmax, Cmin, Cavg, 
AUC0-8h,  CL/Fss, Vz/Fss, RCmax, R AUC, AUClast, AUCinf, λz, 
t1/2, and MR_AUC0-8h will be estimated.  
Additional PK parameters maybe calculated if it deemed 
necessary.  
The placebo arms will be combined for all descriptive summaries 
of subject disposition, demography and Baseline characteristics, 
PD, VOCs, and safety. 
ANC, CANs (count and % neutrophils), and serum CD62L levels 
will be summarized by treatment with quantity and change from 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 13 of 77 
 
Baseline (pre-dose at Day 1) at each visit for which they are 
collected. 
iFABP, LPS, hsCRP, and urine 3-indoxyl sulfate levels will be 
summarized by treatment with descriptive statistics and change 
from Baseline (pre-dose at Day 1) at each visit. 
A dose-response analysis may be conducted to determine the 
relationship between daily rifaximin ER and DER dosing and 
reduction of CANs. Dose-response relationships following the 
final dose on  Day 29 may also be assessed for other PD 
endpoints, if warranted.  
The relationship between rifaximin PK parameters (Ctrough, Cmax,ss, 
Css,avg) and each PD endpoint ( ANC, CANs, serum CD62L levels, 
serum iFABP, serum LPS, serum hsCRP, and urine 3-inoxyl 
sulfate) may be evaluated following the final dose on Day 29.  
Additionally, a population PK/PD model may be developed as a 
separate analysis to explore exposure-response.  If conducted, this 
analysis will be reported separately from the Clinical Study 
Report. 
Safety:  
All AEs occurring during the study will be recorded and classified 
based on MedDRA terminology. Adverse events that occur after 
the start of treatment (treatment-emergent adverse events 
[TEAEs]), will be summarized; all AEs will be included in by-
subject listings.  
TEAEs will be summarized for the entire population, by treatment 
group, and by severity and relationship to study medication. Each 
subject will be counted only once within a system organ class or a 
preferred term by using the adverse event with the highest severity 
or greatest relationship, respectively, within each category. All 
SAEs, AEs leading to premature withdrawal from the study, and 
all deaths will be listed. 
Vital signs will be summarized at Baseline and for each visit. 
Changes from Baseline in vital sign measurements will also be 
summarized.  
Clinical safety laboratory data will be summarized at Baseline, at 
each visit, and as changes from Baseline in laboratory parameters. 
Abnormal findings in ECGs and physical examinations will be 
summarized and listed.  
Data permitting, the number and duration of VOCs (overall and by 
subcategory) and SCD-associated medical facility visits that do 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 14 of 77 
 
not meet the definition of a VOC may be summarized by 
treatment with descriptive statistics. 
Use of opioids, both intravenous and oral, may be summarized by 
treatment group.  By-subject listings will include the opioid, route 
of administration, dose, and duration of treatment. Summaries will 
include descriptive statistics for oral and intravenous use, as well 
as morphine milligram equivalents (MME). 
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 15 of 77 
 
TABLE OF CONTENTS 
 
TITLE PAGE .................................................................................................................................1 
SPONSOR APPROVAL PAGE ...................................................................................................3 
INVESTIGATOR PROTOCOL AGREEMENT .......................................................................4 
SYNOPSIS ......................................................................................................................................5 
TABLE OF CONTENTS ............................................................................................................15 
LIST OF APPENDICES .............................................................................................................18 
LIST OF ABBREVIATIONS .....................................................................................................19 
1.0 
INTRODUCTION............................................................................................................21 
1.1 
Disease Background...............................................................................................21 
1.2 
Rationale for the Use of Rifaximin in the Treatment of Vaso-Occlusive Crises 
in Patients with Sickle Cell Disease.......................................................................22 
2.0 
OBJECTIVES AND ENDPOINTS ................................................................................25 
2.1 
Objectives ..............................................................................................................25 
2.2 
Endpoints ...............................................................................................................25 
2.2.1 
Pharmacokinetics and Pharmacodynamics ...........................................25 
2.2.2 
Safety.....................................................................................................26 
2.2.3 
Exploratory Assessments ......................................................................26 
3.0 
INVESTIGATIONAL PLAN .........................................................................................28 
3.1 
Overview of Study Design .....................................................................................28 
3.2 
Treatment Assignment/Randomization .................................................................28 
3.3 
Procedures for Breaking the Blind .........................................................................29 
4.0 
SELECTION AND WITHDRAWAL OF SUBJECTS ................................................30 
4.1 
Inclusion Criteria ...................................................................................................30 
4.2 
Exclusion Criteria ..................................................................................................31 
4.3 
Concomitant Therapies ..........................................................................................33 
4.3.1 
Prohibited Medications and Therapies ..................................................33 
4.3.2 
Concomitant Procedures .......................................................................34 
4.4 
Females of Reproductive Potential ........................................................................34 
4.5 
Premature Subject Discontinuation........................................................................34 
4.6 
Subject Replacement ..............................................................................................35 
5.0 
STUDY DRUG FORMULATION AND SUPPLY .......................................................36 
5.1 
Packaging and Labeling .........................................................................................36 
5.2 
Storage and Handling .............................................................................................36 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 16 of 77 
 
5.3 
Dosing and Dosing Schedule .................................................................................36 
5.4 
Rationale for Dose Selection .................................................................................37 
5.5 
Study Drug Accountability ....................................................................................37 
5.6 
Assessment of Compliance ....................................................................................38 
6.0 
STUDY PROCEDURES AND ASSESSMENTS ..........................................................39 
6.1 
Study Schedule by Treatment Visit .......................................................................39 
6.1.1 
Visit 1; Screening (Day –21 to Day –1) ................................................39 
6.1.2 
Visit 2; Randomization (Day 1) ............................................................40 
6.1.3 
Visit 3, (Day 8 ±1 day) and Visit 4, (Day 15 ±1 day) ...........................41 
6.1.4 
Visit 5, (Day 29 ±1 day) EOT/ET Visit ................................................42 
6.1.5 
Visit 6 (Day 30) .....................................................................................42 
6.1.6 
Visit 7 (Day 31) .....................................................................................43 
6.1.7 
Visit 8 (Day 32) .....................................................................................43 
6.1.8 
Visit 9 (Day 43 ± 3 days) EOS Visit .....................................................43 
6.1.9 
Visit to a Medical Facility for a VOC Event.........................................44 
6.1.10 
Unscheduled Visit .................................................................................44 
6.2 
Outcome Assessments ...........................................................................................45 
6.2.1 
Assessment of Pharmacokinetics ..........................................................45 
6.2.2 
Assessments of Pharmacodynamics ......................................................46 
6.2.3 
Assessment of Safety ............................................................................46 
6.2.3.1 
Clinical Laboratory Tests ...............................................................46 
6.2.3.2 
Pregnancy Tests .............................................................................48 
6.2.3.3 
Adverse Events ..............................................................................48 
6.2.3.4 
Vital Signs ......................................................................................49 
6.2.3.5 
Electrocardiogram (ECG) ..............................................................49 
6.2.3.6 
Physical Examination.....................................................................49 
6.3 
Other Assessments .................................................................................................49 
6.3.1 
Assessment of VOCs ............................................................................49 
6.3.2 
Medical History .....................................................................................49 
7.0 
SAFETY REPORTING...................................................................................................50 
7.1 
Operating Definitions for Assessing Safety ...........................................................50 
7.1.1 
Adverse Event .......................................................................................50 
7.1.2 
Serious Adverse Event ..........................................................................50 
7.2 
Clinical Laboratory Abnormalities and Other Abnormal Assessments as AEs 
and SAEs ................................................................................................................52 
7.3 
Adverse Events That Are VOC Endpoint Events ..................................................52 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 17 of 77 
 
7.4 
Method, Frequency, and Time Period for Detecting AEs and SAEs.....................53 
7.4.1 
Time Period for Detecting and Reporting of AEs and SAEs ................53 
7.4.2 
Post-Study SAEs ...................................................................................53 
7.5 
Documenting AEs and SAEs .................................................................................53 
7.6 
Common Terminology Criteria for Adverse Events ..............................................54 
7.7 
Assessment of Causality ........................................................................................55 
7.8 
Follow-up of AEs and SAEs ..................................................................................56 
7.9 
Prompt Reporting of SAEs to Salix Pharmaceuticals, Inc. ....................................57 
7.10 
Pregnancy Reporting ..............................................................................................57 
7.11 
Transmission of SAE Report Forms and Pregnancy Report Forms ......................57 
7.12 
Contraception Requirements ..................................................................................58 
8.0 
STATISTICAL CONSIDERATIONS ...........................................................................59 
8.1 
Randomization .......................................................................................................59 
8.2 
Sample Size ............................................................................................................59 
8.3 
Analysis Populations ..............................................................................................59 
8.4 
Analysis Methods...................................................................................................59 
8.4.1 
Methods of Analysis .............................................................................59 
8.4.2 
Subject Disposition ...............................................................................60 
8.4.3 
Demographics and Baseline Characteristics .........................................60 
8.4.4 
Pharmacokinetics ..................................................................................60 
8.4.5 
Pharmacodynamics ...............................................................................61 
8.4.6 
Analysis of Safety .................................................................................61 
8.4.7 
Clinical Safety Laboratory Findings .....................................................62 
8.4.8 
ECG Findings ........................................................................................62 
8.4.9 
Physical Examinations ..........................................................................63 
8.4.10 
Protocol Deviations ...............................................................................63 
8.4.11 
Treatment Compliance ..........................................................................63 
8.4.12 
Treatment Exposure ..............................................................................63 
8.4.13 
Missing Data .........................................................................................63 
8.5 
Statistical and Analytical Issues .............................................................................63 
8.5.1 
Adjustment for Covariates ....................................................................63 
8.5.2 
Interim Analyses and Data Monitoring .................................................63 
8.5.3 
Multicenter Study ..................................................................................63 
8.5.4 
Noncompartmental Analysis of Rifaximin and 25-desacetyl 
rifaximin ................................................................................................63 
9.0 
STUDY ADMINISTRATION ........................................................................................64 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 18 of 77 
 
9.1 
Investigator Information and Training ...................................................................64 
9.2 
Monitoring .............................................................................................................64 
9.3 
Audits .....................................................................................................................64 
10.0 
ETHICAL AND LEGAL ASPECTS .............................................................................65 
10.1 
Institutional Review Board/Ethics Committee (IRB/EC) Approval ......................65 
10.2 
Subject Information and Informed Consent ...........................................................66 
10.3 
Study and Site Closure or Discontinuation ............................................................67 
10.3.1 
Study Discontinuation ...........................................................................67 
10.3.2 
Study Site Discontinuation ....................................................................68 
10.4 
Handling and Record Keeping ...............................................................................68 
10.4.1 
Case Report Forms and Database Processing .......................................68 
10.4.2 
Source Documents ................................................................................68 
10.4.3 
Subject Tracking ...................................................................................69 
10.4.4 
Study Files .............................................................................................69 
10.4.5 
Data Management .................................................................................69 
10.5 
Confidentiality .......................................................................................................69 
10.6 
Record Retention ...................................................................................................69 
10.7 
Financing and Insurance ........................................................................................70 
10.7.1 
Finance ..................................................................................................70 
10.7.2 
Insurance and Indemnification ..............................................................70 
10.8 
Publication Policy ..................................................................................................70 
10.9 
Ownership ..............................................................................................................71 
11.0 
REFERENCES .................................................................................................................72  
 
 
 
 
 
 
LIST OF APPENDICES 
APPENDIX 1: 
Schedule of Assessments .................................................................................73 
APPENDIX 2: 
Schedule for Acquisition of PK Samples.........................................................75 
APPENDIX 3: 
Prohibited CYP3A4 and P-gp and OATP1B1/B3 Inhibitors/Inducers ............76 
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 19 of 77 
 
LIST OF ABBREVIATIONS 
Abbreviation 
Definition 
ABX 
Antibiotics 
ANC 
Absolute neutrophil count 
ACS 
Acute chest syndrome 
ADL 
Activities of daily living 
AE 
Adverse event 
ALT 
Alanine aminotransferase 
BID 
Twice daily 
BP 
Blood pressure 
CBC 
Complete blood count 
CAN 
Circulating aged neutrophils 
CDAD 
Clostridium difficile-associated diarrhea 
CKD-EPI 
Chronic Kidney Disease Epidemiology Collaboration 
COVID-19 
Corona virus disease 2019 
CTCAE 
Common Terminology Criteria for Adverse Events 
DER 
Delayed extended release 
DIC 
Disseminated intravascular coagulation 
EC 
Ethics Committee 
ECG 
Electrocardiogram 
ECOG 
Eastern Cooperative Oncology Group 
eCRF 
Electronic case report form 
EDC 
Electronic data capture 
EOS 
End of study 
EOT 
End of treatment 
ER 
Extended release 
ET 
Early termination 
FDA  
Food and Drug Administration 
GCP 
Good Clinical Practices 
GFR 
Glomerular filtration rate 
Hb 
Hemoglobin  
HBcAb 
Hepatitis B core antibody 
HBsAg 
Hepatitis B serum antigen 
HC 
Hydroxycarbamide 
HCV 
Hepatitis C-virus 
HR 
Heart rate 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 20 of 77 
 
Abbreviation 
Definition 
hsCRP 
High sensitivity C-reactive protein 
HU 
Hydroxyurea 
ICF 
Informed Consent Form 
ICH 
International Conference on Harmonization 
iFABP 
Intestinal fatty-acid binding protein 
INR 
International normalized ratio 
IOA 
Intravenous opioid analgesic 
IRB 
Institutional Review Board 
ITP 
Idiopathic thrombocytopenia purpura 
LPS 
Lipopolysaccharide 
LTFU 
Lost to follow up 
MedDRA 
Medical Dictionary for Regulatory Activities 
MME 
Morphine milligram equivalents 
NCA 
Non-compartmental analysis 
NSAID 
Non-steroidal anti-inflammatory drug 
PD 
Pharmacodynamics 
PHI 
Protected health information 
PK 
Pharmacokinetics 
PPI 
Proton pump inhibitor 
RBC 
Red blood cell 
RNA 
Ribonucleic acid 
SAE  
Serious adverse event 
SAP 
Statistical analysis plan 
SCA 
Sickle cell anemia 
SCD 
Sickle cell disease 
SCT 
Stem cell transplant 
SD 
Standard deviation 
TEAE 
Treatment-emergent adverse event 
ULN 
Upper limit of normal 
US 
United States 
3-IS Urine 
Urine 3-indoxyl sulfate 
VOC 
Vaso-occlusive crisis 
WOCBP 
Women of child-bearing potential 
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 21 of 77 
 
1.0 
INTRODUCTION 
1.1 
Disease Background  
Sickle cell disease (SCD) is a related group of common and rare hemoglobin (Hb) genotypes in 
which all affected individuals are either homozygotes for the sickle Hb (HbS) mutation of the β-
globin subunit or compound heterozygotes for HbS and another globin gene mutation 
[Steinberg 2012]. The various forms of SCD are based on inheritance patterns from an individual’s 
parents. The most common type of SCD, HbSS features two sickle cell genes (“S”); one “S” gene 
is inherited from each parent. HbSS genotype presents as sickle cell anemia (SCA) and is the most 
severe form of SCD. Another common yet milder type of SCD is HbSC. A single sickle cell gene 
(“S”) is inherited from one parent, and an abnormal Hb gene “C” is inherited from the other parent. 
A third type of SCD is HbS β-thalassemia. In this genotype, a single sickle cell gene (“S”) is 
inherited from one parent and another gene for β-thalassemia is inherited from the other parent. 
HbS β-thalassemia can be further divided into two subtypes: subtype HbS β0-thalassemia, which 
is a more severe form of SCD, and subtype HbS β+-thalassemia, which is a milder form of SCD. 
Individuals with the sickle cell trait (HbAS) generally do not exhibit signs and symptoms of SCD. 
In this genotype, a single sickle cell gene is inherited from one parent. However, a normal gene 
“A” is inherited from the other parent. Nevertheless, there is the risk of passing the sickle cell gene 
to offspring [CDC 2020; da Guarda 2020; Steinberg 2012]. 
Hb in SCD has the physical tendency for polymerization in deoxygenated conditions.  Among the 
many changes that result from the damage to the sickle RBC (SS-RBC) membrane is the 
propensity to adhere to the vascular endothelium.  SS-RBCs and activated endothelial cells can 
produce a proinflammatory environment that is exacerbated during episodes of vaso-occlusive 
crisis (VOC) [Manwani 2013]. SS-RBCs are rigid and do not easily flow through the 
microcirculation; they exhibit changes in solubility and molecular stability and can obstruct the 
vasculature, resulting in the clinical manifestations of SCD [Darbari 2020].  
A hallmark symptom of SCD is a painful VOC. An interplay of the various pathologic processes 
in SCD perpetuates and feeds forward an inflammatory priming that, in the presence of a 
precipitating event, can lead to a VOC. Precipitating events for a VOC may include hypoxia, 
infection, dehydration, acidosis, alcohol intoxication, emotional stress, pregnancy, and cold 
weather (vasospasm).  A VOC is initiated and sustained by interactions among sickle cells, 
endothelial cells, and plasma constituents. There is a cytokine mediated exchange implicated in 
the development of a VOC between sickled erythrocytes, aged and activated neutrophils, 
inflammatory messenger molecules, monocytes, platelets, and endothelium. Activated neutrophils 
play a pivotal role in initiating a VOC and act as central elements during the crisis. Higher 
neutrophil counts correlate with more severe disease manifestation, including earlier death, 
increased incidence of silent brain infarcts, hemorrhagic stroke, and acute chest syndrome (ACS) 
[Darbari 2020, Lim 2016].  
VOCs are responsible for a wide variety of clinical complications of SCD, including pain 
syndromes, acute chest syndrome (ACS), stroke, priapism, leg ulcers, spontaneous abortion, renal 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 22 of 77 
 
insufficiency, and multiorgan failure leading to death. Frequency of VOCs, along with ACS, is the 
most common predictor of death in patients with SCD. Thus, early identification, treatment, and 
prevention of VOCs could significantly impact the natural course of the disease. During a VOC, 
patients present with acute severe pain that is often described as throbbing and sharp. Common 
sites of pain include the lower back, joints, and extremities [Darbari 2020, Yale 2000].  
1.2 
Rationale for the Use of Rifaximin in the Treatment of Vaso-Occlusive Crises in 
Patients with Sickle Cell Disease  
Recent studies have identified various cellular and molecular factors that contribute to the 
pathophysiology of SCD. These include the complex interaction between erythrocytes, platelets, 
vascular endothelial surface molecules, and neutrophils. Both activated and aged neutrophils may 
be immobilized on vascular endothelium and form the nidus for sickled erythrocytes to adhere, 
eliciting a VOC [Zhang 2016, Lim 2019]. 
Circulating aged neutrophils (CANs), a subset of neutrophils with high surface expression of 
CXCR4 and low CD62L (L-selectin), may be significantly elevated during a VOC. CD62L is shed 
on neutrophil activation and acts as a sensitive marker. The expression of CD62L on neutrophils 
decreases in patients with SCD experiencing a VOC [Lard 1999].  
In several scientific experiments, Zhang, et. al. demonstrated a relationship between the 
microbiome and neutrophil aging/activation. Treatment of mice with broad-spectrum antibiotics 
(ABX) led to a highly efficient depletion and dramatic alterations in the composition of the gut 
microbiota. Microbiota depletion resulted in significant and selective reductions of neutrophil 
numbers in the circulation. Both the percentages and numbers of aged neutrophils were 
significantly reduced in ABX-treated mice. To assess the role of neutrophil aging in an applicable 
model, genetically engineered mice with SCD were studied. SCD mice exhibited expansion of all 
major white blood cell subsets compared with healthy control mice. ABX-mediated microbiota 
depletion led to a significant and specific decrease of neutrophils, but not the other leukocyte 
populations. Importantly, in mice with SCD, aged neutrophils populations were increased by > 10-
fold, and their expansion was completely negated by microbiota depletion [Zhang 2015]. 
Therefore, modulating intestinal microbial composition may be a therapeutic option in SCD to 
reduce VOC by decreasing both activated and aged neutrophils.  
Lim, et. al. hypothesized that an intestinal dysbiosis is associated with VOC episodes characteristic 
of SCD. Abnormalities in the integrity of the intestinal wall/mucosa, a chronic dysbiosis of the 
intestinal flora, or both are likely to occur in patients with SCD. The intestinal mucosa and the 
ability of the gut wall to support a normal microbiome in patients with SCD are impaired, due to 
periodic or global low-grade intestinal ischemia that occurs as a result of VOCs in the splanchnic 
vasculature. The compromised intestinal barrier renders patients with SCD more susceptible to 
recurrent translocation of intestinal bacteria into the submucosa and bloodstream. Although the 
bacterial inocula are not numerous enough to cause overt infections, they can activate an immune 
response [Lim 2016, Lim 2018].  

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 23 of 77 
 
Frequent microbial and pathophysiologic changes have been observed in the intestines of patients 
with SCD, including enterocyte injury, altered microbial composition, increased permeability, and 
bacterial overgrowth. Dutta, et. al. measured serum intestinal fatty-acid binding protein (iFABP) 
and lipopolysaccharides (LPS) levels in patients with SCD. Both iFABP and LPS are markers for 
intestinal injury and impaired bowel wall integrity (“leaky gut”).  Levels were then compared to 
patients with iron deficiency anemia, but without SCD. Individuals with SCD had significantly 
higher iFABP (P = 0.04) and LPS (P = 0.03), indicating intestinal injury and increased intestinal 
bacterial translocation into the systemic circulation. In addition, serum soluble CD62L (P = 0.04) 
was elevated, and soluble CD62L correlated positively with CANs (R = 0.7, P = 0.03) and LPS (R 
= 0.66, P = 0.027).  These results provide evidence of the presence of intestinal compromise and 
increased gut permeability in patients who have SCD [Dutta 2019].  It has been demonstrated that 
rifaximin modulation of ileal microbiome communities prevents impairment of intestinal barrier 
function induced by chronic stress. [Xu 2014].  
Lim, et al, also hypothesized that rifaximin is an ideal antimicrobial agent for gut decontamination 
in patients with SCD and will reduce hospital admissions due to painful VOC through modification 
of the intestinal microbiome and a reduction of CANs. In August 2019, Lim et al completed a 
single-arm, open-label study of 13 adult patients with SCD (HbSS, HbSC, HbS β-thalassemia), 
administered rifaximin 550 mg BID for 6 months (NCT03719729). The primary objective of the 
study was to determine the feasibility and toxicity profile of long-term rifaximin in patients with 
SCD [Dutta 2020, Lim 2019].  
Results from the Phase 2 study demonstrated that treatment with rifaximin significantly reduced 
the frequency of painful VOCs and the number of days patients needed IOA compared with the 
prior 12 months when patients were not on rifaximin therapy. In the 12 patients evaluated, there 
was a mean decrease from the expected 2.25 VOCs (range 1–6.5) per 6 months to 1 VOC per 6 
months (range 0–4) in patients receiving rifaximin (P = 0.003). There was also a significant 
decrease with rifaximin in days needing IOA over the 6-month study period (median 9 days; range 
1–55; P = 0.008). Furthermore, the total number of days that patients with SCD required IOA was 
reduced from the expected 254 days over 6 months to 98 days during the 6-month rifaximin 
treatment period.  
Serum CD62L was serially measured and found to be elevated in 9 patients at baseline, but then 
consistently declined to levels observed in non-SCD controls (P < 0.001). In addition, most (75%) 
patients exhibited > 10% CANs in their venous blood before starting rifaximin (median 12.6; range 
6–40) and levels of CANs dropped significantly in all patients after starting rifaximin to below 5% 
(P = 0.005). Drops in CANs occurred as early as 2 weeks after initiation of rifaximin and remained 
low throughout the 6-month study period.  Likewise, baseline serum iFABP was elevated in all 
patients and decreased significantly (P = 0.008) with rifaximin in all patients to levels comparable 
with non-SCD controls.  
Overall, rifaximin was well tolerated. Mild nausea was common in the first 1–2 weeks of therapy 
and occurred in 8 patients. Other adverse events included self-limiting diarrhea (n = 1), which 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 24 of 77 
 
occurred during the first month of therapy and polydipsia (n = 2). No episodes of Clostridium 
difficile colitis were reported. Laboratory analyses did not show any significant change in Hb, 
white cell counts, serum lactate dehydrogenase, bilirubin, or haptoglobin due to rifaximin therapy 
[Lim 2019].  This was the first study in humans showing the potential efficacy of microbial 
modulation on VOCs in patients with SCD and forms the basis for further investigation.  
Rifaximin extended release (ER) and delayed extended release (DER) Capsules are new 
pharmaceutical formulations designed to have better dissolution properties within the lumen of the 
gut to target different areas of the GI tract.  The ER Capsule is a controlled release solid oral dosage 
form designed to target delivery of rifaximin to the upper GI tract, and the DER Capsule is a 
controlled release solid oral dosage form designed to target delivery of rifaximin to the mid-GI 
tract. 
The current study is designed to evaluate the PK of ER and DER Capsules and to assess the 
response to treatment of PD markers associated with VOCs including ANC, CANs, serum CD62L, 
hsCRP, the gut permeability biomarkers iFABP and LPS, and the gut bacteria biomarker urine 
3-indoxyl sulfate in subjects with SCD.  The safety and tolerability of these new formulations will 
also be evaluated in this patient population. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 25 of 77 
 
2.0 
OBJECTIVES AND ENDPOINTS 
2.1 
Objectives 
The objectives of this study are: 
• To characterize the pharmacokinetics/pharmacodynamics (PK/PD) of rifaximin ER and 
DER in subjects with sickle cell disease (SCD)  
• To assess the safety and tolerability of rifaximin ER and DER 
2.2 
Endpoints 
2.2.1 
Pharmacokinetics and Pharmacodynamics 
Full rifaximin and 25-desacetyl rifaximin plasma PK profiles following administration on Days 1 
and 29 and Cmax and Ctrough on Days 8, 15, and 29 will be evaluated.  
Blood samples for PK analysis will be collected at the following timepoints: 
• Day 1 and Day 29: pre-dose, 0.5, 1, 1.5, 2, 3, 4, 5, and 8-hours post-dose.  
• Day 8 and Day 15: pre-dose and 0.5, 1, and 2-hours post-dose. 
• Day 29: pre-dose, 0.5, 1, 1.5, 2, 3, 4, 5, and 8-hours post-final dose 
• Day 30: 24 and 30 hours post-final dose 
• Day 31: 48 hours post-final dose 
• Day 32: 72 hours post-final dose 
• During medical facility visit for VOC with estimated time of last dose, when possible.  
PD biomarkers (ANC, CANs, serum CD62L, hsCRP, the gut permeability biomarkers serum 
iFABP and LPS, and the gut bacteria biomarker urine 3-indoxyl sulfate) will be collected at the 
following timepoints: 
• Day 1: pre-dose 
• Day 8, Day 15, and Day 29: during each visit – pre dose 
• Day 31  
• Day 43 
• During medical facility visit for VOC, when possible. 
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 26 of 77 
 
2.2.2 
Safety  
Safety will be assessed throughout the duration of the study by collection of adverse events (AEs), 
vital signs (systolic and diastolic blood pressure, heart rate, oral body temperature, and oxygen 
saturation), clinical safety laboratory tests (chemistry, coagulation, hematology, urinalysis, and 
high sensitivity C-reactive protein (hsCRP), physical examinations, and electrocardiograms 
(ECGs).  The safety endpoints are the following: 
• Incidence of treatment-emergent adverse events (TEAEs) and serious adverse events 
(SAEs) 
• Clinically significant changes from Baseline in clinical laboratory results 
• Changes from Baseline in vital signs 
2.2.3 
Exploratory Assessments 
Information on any potential VOCs experienced during the study will be collected as follows: 
• Dates and duration of each episode. A VOC is defined as: 
o The occurrence of appropriate symptoms consistent with a painful crisis, acute 
chest syndrome (ACS), or priapism, and  
o Requires visit to a medical facility, and 
o Receipt of either a parenteral or oral opioid or NSAID analgesia. 
• Categorization of VOCs.  Subcategories will consist of: 
o Uncomplicated pain crisis, defined as a painful crisis that is NOT classified as an 
acute chest syndrome, hepatic sequestration, splenic sequestration, or priapism. 
o Acute Chest Syndrome (ACS), defined as a finding of a new pulmonary infiltrate 
involving at least one complete lung segment that was consistent with alveolar 
consolidation, but excluding atelectasis (as indicated by chest X-ray). Must also 
present with at least one of the following signs or symptoms: patient-reported chest 
pain, body temperature of more than 38.5 °C, tachypnea, wheezing, or cough. 
o Hepatic sequestration, defined as findings of right upper quadrant pain, an enlarged 
liver, and an acute decrease in hemoglobin concentration. 
o Splenic sequestration, defined as findings of left upper quadrant pain, an enlarged 
spleen, and an acute decrease in hemoglobin concentration. 
o Priapism, defined as having a sustained penile erection requiring a visit to a medical 
facility. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 27 of 77 
 
• Intravenous opioid analgesia (IOA) and oral opioid use during VOCs, including date/time 
of each start and stop of treatment, dose, drug, inpatient/outpatient setting, and date/time 
of readiness-to-discharge. 
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 28 of 77 
 
3.0 
INVESTIGATIONAL PLAN 
3.1 
Overview of Study Design 
Study RBSC2161 is a Phase 2a, randomized, double-blind, placebo-controlled, multicenter study 
to evaluate the pharmacokinetics (PK), pharmacodynamics (PD) safety and tolerability of 
rifaximin ER and DER in subjects with SCD.  Exploratory assessments of the effect of rifaximin 
ER and DER on the incidence of VOCs will also be explored.   
Approximately 60 subjects who successfully complete the Screening Period will enter the 
Treatment Period and will be randomized to one of six treatment groups.  Approximately 20  study 
centers are expected to participate in the study.   
Objectives and endpoints for the study are provided in Section 2.  Assessments of PK/PD and 
safety, and documentation of VOCs (Appendix 1 and Section 7.3) will be performed during clinic 
visits at Baseline (Day 1), Day 8, Day 15, and Day 29 (End of Treatment/Early Termination).  All 
subjects will also complete an End of Study (EOS) Visit 2 weeks later (Day 43; End of Study) for 
final assessments. Assessments will also be conducted when a subject visits a healthcare facility 
for treatment of a VOC.  If a subject prematurely discontinues treatment, every attempt will be 
made to obtain EOT and EOS assessments and subjects should be followed until the end of the 
43-day trial. 
Before study subjects can be screened, the laboratory where the CANs assessment will be 
performed shall undergo a qualification run. This is to ensure that the flow cytometry assessment 
for CANs can be performed at the local site as outlined in the Laboratory Manual. The qualification 
run will be performed with blood from healthy, adult, non-pregnant, and capable volunteers of 
general good health (and non-sickle cell disease subjects). Approximately 25 healthy volunteers 
(one per site, or per local lab) is expected to participate. Healthy volunteers will visit the study 
center once for this assessment (single blood draw) and it should take no more than 30 minutes to 
complete the testing. 
 
3.2 
Treatment Assignment/Randomization 
Subjects who meet the eligibility criteria and have given written informed consent will be 
randomized in a 2:2:1:2:2:1 allocation to one of 6 treatment groups.  Approximately 12 subjects 
will be randomized to each active rifaximin treatment and approximately 6 subjects to each placebo 
group.  The treatment groups will be run in parallel. 
• Group 1: 40 mg rifaximin ER, BID  
• Group 2: 40 mg rifaximin DER, BID  
• Group 3: Placebo for 40 mg rifaximin, BID  

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 29 of 77 
 
• Group 4: 80 mg rifaximin ER, BID 
• Group 5: 80 mg rifaximin DER, BID  
• Group 6: Placebo for 80 mg rifaximin, BID  
3.3 
Procedures for Breaking the Blind 
Subjects, study staff, and the Sponsor will be aware of the dose groups (2 x 20 mg capsules BID 
or 4 x 20 mg capsules BID) but will be blinded to active or placebo.  Only in the case of an 
emergency, when knowledge of the study drug is essential for the clinical management or welfare 
of the subject, will the Investigator be allowed to unblind a subject’s treatment assignment.  To 
discuss breaking of the blind, the Investigator should contact the Medical Monitor.  The 
Investigator will unblind via an Interactive Response Technology system. 
If the Investigator breaks the blind for an individual subject, the reason must be in the subject’s 
source documents and the subject will be removed from the study. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 30 of 77 
 
4.0 
SELECTION AND WITHDRAWAL OF SUBJECTS 
4.1 
Inclusion Criteria 
A subject will be eligible for inclusion in this study if he/she meets all of the following criteria: 
1. Subject must have the ability and willingness to sign a written informed consent form. 
2. Subject is between the ages of 18 to 70 years old (inclusive) at the time of consent. 
3. Subject has SCD of any genotype (HbSS, HbSC, HbS β-thalassemia).  If the subject’s 
genotype has not been previously documented, genotyping will be performed during 
Screening using high-performance liquid chromatography (HPLC)/electrophoresis. 
4. Subject must have experienced at least 2 VOCs within the 12 months prior to Screening. 
A VOC is defined as: 
a. The occurrence of appropriate symptoms consistent with a painful crisis, acute 
chest syndrome (ACS), or priapism, and  
b. Requires a visit to a medical facility and/or healthcare professional, and 
c. Receipt of either a parenteral or oral opioid or NSAID analgesia.  
5. If subject is receiving hydroxyurea (HU)/hydroxycarbamide (HC), subject must have been 
receiving the treatment for at least 6 months prior to Screening and must agree to maintain 
the same dose and schedule for the duration of the study.  
6. Subjects must have laboratory values at Screening within the following ranges: 
o Absolute Neutrophil Count ≥1.0 x 109/L 
o Platelets ≥ 75 x 109/L 
o Hemoglobin (Hgb) ≥ 6.0 g/dL 
o Glomerular filtration rate (GFR) ≥ 45 mL/min/1.73 m2 using the CKD-EPI 
formulaTotal bilirubin ≤ 15 mg/dL 
o Alanine transaminase (ALT) ≤ 3.0 x ULN 
o International Normalized Ratio (INR) ≤ 2.0 
7. Eastern Cooperate Oncology Group (ECOG) performance status ≤ 2. 
8. Women of child-bearing potential, defined as all women physiologically capable of 
becoming pregnant, must have a negative serum pregnancy test at Screening and agree to 
use standard prevention methods for the duration of the study. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 31 of 77 
 
4.2 
Exclusion Criteria 
A subject will not be eligible for inclusion in this study if any of the following criteria apply: 
1. Subject is receiving concomitant treatment with voxelotor, crizanlizumab, or L-glutamine. 
2. Subject has any history of stem cell transplant is planning to begin or has received in the 
past 30 days. 
3. Subject experiences an acute VOC, requiring a visit to a medical facility and/or healthcare 
professional, ending within 7 days prior to Day 1 dosing. 
4. Subject has received any blood products within 30 days of Day 1 dosing. 
5. Subject has uncontrolled liver disease or renal impairment, ulcerative colitis, Crohn’s 
disease, or other chronic GI disorder. 
6. Subject has received active treatment in another investigational trial within 30 days or 5 
half-lives of the last dose of the investigational agent, whichever is greater, prior to 
Screening. 
7. Subject has received penicillin prophylaxis or antibiotics for treatment of infection within 
30 days or 5 half-lives of the treatment, whichever is greater, prior to Screening. 
8. Subject has a significant medical condition that required hospitalization (other than for a 
VOC) within 2 months prior to Screening. 
9. Subject is planning on undergoing an exchange transfusion during the duration of the study 
or has completed one within 4 weeks prior to Day 1 dosing. 
10. Subject has a hypersensitivity to rifaximin, rifampin, rifamycin antimicrobial agents, or 
any components of rifaximin ER and DER. 
11. Subject is pregnant or a nursing woman. 
12. Subject has a history of illicit drug use or abuse, either documented or in the opinion of the 
Investigator. 
13. Subject is using any medication that is known to inhibit or induce CYP3A4,  P-gp, or 
OATP1B1/B3 (See Appendix 3) within 30 days or 5 half-lives, whichever is longer, prior 
to Day 1 dosing, or in the opinion of the Investigator, may affect the evaluation of the study 
product or place the subject at undue risk. 
14. Subject has had any prior gastrointestinal surgery which has altered the anatomy of the 
esophagus, stomach, or small/large intestine (with the exception of appendectomy, 
cholecystectomy, and fundoplication). 
15. Subject has had a colonoscopy or sigmoidoscopy within 30 days prior to Day 1 or plans to 
undergo such a procedure during the duration of the study. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 32 of 77 
 
16. Subject has used bowel prep, laxative, or enema within 30 days prior to Day 1. 
17. Subject has a bleeding disorder including, but not limited to, acquired or congenital platelet 
function defects, disseminated intravascular coagulation (DIC), bleeding factor 
deficiencies, hemophilia, idiopathic thrombocytopenia purpura (ITP), or von Willebrand’s 
disease. 
18. Subject is planning to undergo a major surgical procedure during the duration of the study. 
19. Subject has a positive test for human immunodeficiency virus (HIV)1 or HIV2. 
20. Subject has an active Hepatitis B infection (HBsAg positive).  Prior infection that is not 
active (i.e., HBsAg negative, HBcAb positive, and HBsAb positive) is permitted.  
21. Subject has a positive test for Hepatitis C (HCV RNA).  Prior infection with spontaneous 
resolution or sustained resolution for ≥ 24 weeks after cessation of antivirals is permitted. 
22. Subject has an active COVID-19 infection or complication(s) related to COVID-19 
infection that are unresolved or, in the opinion of the Investigator, may affect evaluation of 
the study drug or place the subject at undue risk. 
23. Subjects has received a vaccine (including COVID-19 vaccine) within 2 weeks prior to 
Screening.  If subject has received their first of two COVID-19 vaccination doses, as 
applicable, they must wait for at least 2 weeks after receiving the second dose, and be 
symptom-free, prior to beginning Screening.  Subject must not be planning for COVID-19 
or other vaccinations while on study.   
24. Subject has a malignant disease.  Exceptions include malignancies that were treated 
curatively and have not recurred within 2 years prior to study treatment, completely 
resected basal cell and squamous cell skin cancers, and any completely resected carcinoma 
in situ. 
25. Subjects has prolonged QT interval as assessed by ECG history within the past 3 months.  
For subjects with no historical ECG information, subject has a resting QTcF ≥ 460 msec 
for males and ≥ 470 msec for females at Screening. 
26. Subject has any unstable cardiac condition that, in the opinion of the Investigator, may 
worsen during the study or interfere with successful evaluation of the study treatment.  
27. Subject has a serious mental or physical illness which, in the opinion of the Investigator, 
would compromise participation in the study. 
28. Subject has any condition which, in the opinion of the Investigator, is likely to interfere 
with the successful collection of the measurements required for the study. 
29. Subject is unable to understand or comply with study instructions and requirements. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 33 of 77 
 
4.3 
Concomitant Therapies 
A concomitant medication is any drug or substance administered between the signing of the 
informed consent and the EOS/ET Visit.  The use of concomitant therapies or procedures must be 
recorded on the subject’s eCRF, according to instructions for eCRF completion. Adverse events 
related to administration of these therapies or procedures must be documented in the appropriate 
eCRF. 
Other than the medications listed in Section 4.3.1, medications that are used as the standard of care 
for SCD will be allowed during the study.  
Use of HU/HC is allowed during the study.  However, subjects receiving should maintain a stable 
dose throughout the study. 
A COVID-19 vaccination is to be recorded as concomitant medication.   
4.3.1 
Prohibited Medications and Therapies 
Treatment with the following is not allowed during the study: 
• Non-study rifaximin (e.g., commercial rifaximin, XIFAXAN® 550 mg tablets), 
rifampin or other rifamycin derivatives are prohibited within 30 days of providing 
consent, and throughout the study.  
• Initiation of treatment with HU/HC, voxelotor, crizanlizumab, or L-glutamine. 
• COVID-19 vaccination.   
• Gene therapy for SCD. 
• Initiation of a chronic transfusion program (pre-planned series of transfusions for 
prophylactic purposes). 
• Enrollment in any other drug, biologic, or device clinical study or treatment with an 
approved therapy for investigational development or unapproved investigational drug 
under development is not allowed. 
• Chronic antibiotic use throughout the study is prohibited.  A short-course of antibiotic 
therapy (≤ 7 days; non-rifamycin and non-quinolone classes only) to treat infections 
such as sinusitis, urinary tract infections, etc. or for dental therapy prophylaxis is 
permitted.  Longer courses of therapy will require the permission of the Sponsor. 
• Treatment with CYP3A4 inhibitors/inducers, P-glycoprotein (P-gp) 
inhibitors/inducers, and organic anion transporting polypeptide (OATP1B1/B3) 
inhibitors shown in Appendix 3.  
• Use of proton pump inhibitors (PPIs).   
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 34 of 77 
 
4.3.2 
Concomitant Procedures 
A concomitant procedure is any therapeutic intervention (eg, surgery/biopsy, physical therapy) or 
diagnostic assessment (eg, blood gas measurement, bacterial cultures) performed between the time 
the subject is enrolled in the study and the EOS/ET Visit. 
Subjects are not to receive a stem cell transplant during the study.  
Subjects are not to undergo elective surgeries during the study. 
4.4 
Females of Reproductive Potential 
There are no adequate and well controlled studies in pregnant women.  Rifaximin has been shown 
to be teratogenic in rats and rabbits at doses that caused maternal toxicity.  
Women of childbearing (reproductive) potential must have a negative serum pregnancy test at 
Visit 1 (Screening) and negative urine pregnancy test at Visit 2 prior to randomization on Day 1. 
These subjects must agree to use an acceptable method of contraception throughout their 
participation in the study (see details in Section 7.12).  If a female subject becomes pregnant while 
on this study, the study drug will be immediately discontinued, and the subject will be followed 
until the outcome of the pregnancy is known.  The pregnancy will be reported to Salix using the 
guidelines provided in Section 7.10 and Section 7.11. 
4.5 
Premature Subject Discontinuation 
All subjects are free to withdraw from participating in this study at any time for any reason, 
specified or unspecified, and without prejudice.  No constraints will be placed on ordinary subject 
management, and subjects, when appropriate, will be placed on other conventional therapy upon 
request or whenever clinically necessary as determined by their physician.  
Withdrawal of the subject from treatment with study drug or from the study will be considered, in 
consultation with the Sponsor, or designee, for any of the following reasons: 
• The subject withdraws consent. 
• The subject experiences an intolerable AE or SAE. 
• The subject experiences CDAD  
• The subject enrolls into another interventional clinical study in which an investigational 
treatment or approved therapy for investigational use is administered. 
• The subject becomes pregnant.  Study treatment must be discontinued immediately. 
Report the pregnancy according to the instructions in Section 7.10. 
• The subject is unwilling or unable to comply with the protocol. 
• At the discretion of the Investigator or Sponsor.  

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 35 of 77 
 
• Investigator decision that it is not in the best medical interest of the subject to continue 
participation in the investigation. 
Prior to discontinuing a subject, every effort should be made to obtain as much follow-up data as 
possible.  Withdrawn or discontinued subjects will undergo early termination procedures per the 
scheduled assessments for the Early Termination (ET) Visit.  AEs will be followed as described 
in Section 7.8.  Subject withdrawals will be documented clearly on the source documents and 
applicable eCRFs.  
Notification of subject withdrawals will be made to the Sponsor, or designee. 
4.6 
Subject Replacement 
Subjects that are withdrawn, terminate the study early (including for an AE), or are lost to follow-
up (LTFU) during the study may be replaced to ensure appropriate number of subjects complete 
the study.  The decision to replace a subject will be made in agreement between the Sponsor and 
Investigator. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 36 of 77 
 
5.0 
STUDY DRUG FORMULATION AND SUPPLY 
Rifaximin ER and DER are supplied as 20 mg capsules.  Subjects will be randomized to receive 
either 40 mg or 80 mg of ER or DER and matching placebo capsules for the duration of the study. 
5.1 
Packaging and Labeling 
Outer packaging and capsules will be packaged and labeled in a manner consistent with the study 
design and according to applicable national / regional and local regulations for an investigational 
drug. 
Each unit of rifaximin ER and DER capsules and placebo capsules will bear a label that meets 
applicable laws for an investigational drug, which includes, but is not limited to, the following 
information: 
• Protocol Number 
• Kit Number 
• A statement reading: “Caution: New Drug Limited by Federal Law to Investigational Use” 
• A statement reading, “Manufactured for Salix Pharmaceuticals, Inc., a division of Bausch 
Health US, LLC” 
• Recommended storage conditions. 
5.2 
Storage and Handling 
All study drug will be kept in a locked area with limited access.  All units of study drug must be 
stored at 20º-25º C (68º-77º F) with excursions of 15º-30º C (59º-86º F) permitted.  Study drug 
will be dispensed by qualified study staff only in accordance with the procedures described in this 
protocol. 
5.3 
Dosing and Dosing Schedule 
Each subject will be dispensed study drug at each visit with enough capsules to dose through their 
next visit. 
During the Treatment Period, eligible subjects will take study drug BID according to their 
treatment assignment as outlined in Table 1.  Dosing will begin on Study Day 1 (Visit 2) and 
continue through Study Day 29 (Visit 5).  Doses will be taken orally with water, and capsule will 
be swallowed whole. Study participants should be instructed to take the study drug on an empty 
stomach. The morning (AM) dose should be taken on an empty stomach, and subjects must avoid 
food for two hours after taking the study drug. The evening (PM) dose should be taken on an empty 
stomach (at least two hours after the last meal), and subjects must avoid food for two hours after 
taking the study drug.  

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 37 of 77 
 
On Days 1, 8, 15, and 29, participants will fast for a minimum of 10 hours prior to, and 2 hours 
after, the morning study drug administration. Water will be restricted from one hour prior to dosing 
through one hour following dosing, except for the water that will be consumed at dosing. Study 
drug should be administered with approximately 240 mL of water. 
Table 1   Dosing by Treatment Assignment 
Dose 
Group Formulation Study Day 
Total Number of 
Capsules 
Capsule 
(mg) 
Daily Dose 
(mg) 
No. of 
Subjects 
1 
ER 
Daily 
4 (2 in AM, 2 in PM) 
20 
80 
12 
2 
DER 
Daily 
4 (2 in AM, 2 in PM) 
20 
80 
12 
3 
Placebo 
Daily 
4 (2 in AM, 2 in PM) 
20 
- 
6 
4 
ER 
Daily 
8 (4 in AM, 4 in PM) 
20 
160 
12 
5 
DER 
Daily 
8 (4 in AM, 4 in PM) 
20 
160 
12 
6 
Placebo 
Daily 
8 (4 in AM, 4 in PM) 
20 
- 
6 
Note: AM and PM refer to approximate 12-hour period between doses   
Before any study drug is administered, each subject will be instructed by the Investigator or his/her 
representative on the proper self-administration of study drug.  All unused study drug will be 
returned to the study site at the next clinic visit. 
5.4 
Rationale for Dose Selection 
The dose and formulation of rifaximin ER and DER formulations selected for this study are based 
on the safety of these formulations observed in the Phase 1 healthy volunteer study, RBPK 1001 
and on the safety of rifaximin in clinical studies supporting the approval of XIFAXAN®.  For 
additional details on the safety of the ER and DER formulations and on XIFAXAN refer to the 
Investigators’ Brochure.    
5.5 
Study Drug Accountability 
All study drug will be kept in a secure, temperature-controlled area with limited access.  
Investigational drug orders, records of study drug receipt, dispensing, re-dispensing, returned study 
drug, and running inventory will be examined and reconciled throughout the study.  Upon the 
completion of the study, all material will be subjected to final inspection and reconciliation.  
Instructions will be provided by the Sponsor regarding final disposition of all study medication in 
compliance with applicable regulations. 
Study drug reconciliation will be conducted during monitoring visits to ensure appropriate receipt, 
storage, dispensing, and documentation of returned study drug. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 38 of 77 
 
5.6 
Assessment of Compliance 
After study drug is dispensed, the Investigator or his/her representative will count and record the 
unused study drug capsules that are returned by the subject at each visit.  If the subject forgets to 
return unused study drug at a visit, then compliance will be confirmed after direct questioning of 
the subject. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 39 of 77 
 
6.0 
STUDY PROCEDURES AND ASSESSMENTS 
The schedule of assessments to be performed during the study is provided in Appendix 1, Schedule 
of Assessments, and Appendix 2, Schedule for Acquisition of PK Samples.  For this study, Day 1 
(Visit 2), which is the day of randomization, shall be defined as the subject’s Baseline.   
Note: Prior to screening study subjects, the flow cytometry assessment (including healthy 
volunteers) will need to be certified at the laboratory where the assessment will be completed.  
In case of situations that prevent a participant from attending a post-baseline study visit, a home 
health visit may be scheduled, where possible. The home health visit may include an assessment 
of changes in health and medications, measurement of vital signs and body weight, and checking 
of study medication compliance. The home health visit may also include all sample collections 
outlined in the study protocol (PK, hematology and urinalysis samples, urine sample for urine 3-
inoxyl sulfate, and blood samples for CANs (if applicable), CD62L, iFABP and LPS).  
All documented assessments and laboratory results will be reviewed by the investigator and 
documented in relevant eCRFs as appropriate. 
6.1 
Study Schedule by Treatment Visit 
6.1.1 
Visit 1; Screening (Day –21 to Day –1) 
The initial Screening Visit (Visit 1) should be conducted between Days -21 and -1, inclusive.  The 
following procedures are to be completed at Visit 1: 
• Obtain informed Consent signed by the subject prior to performing any study evaluations 
or procedures including asking subjects to discontinue any prohibited medications. 
• Record demographics and medical history information.  Detailed history of VOCs 
occurring over the past 12 months will be obtained. This will include collection of 
treatments for VOCs including drug, dose, route of administration, duration of treatment, 
and inpatient/outpatient setting.   
• Record all opioid use within the 30 days prior to Screening. 
• Review Inclusion/Exclusion criteria to ensure subject qualifies for the study. 
• Obtain height and weight. 
• Obtain vital sign measurements.  Vital signs to be collected are blood pressure (BP) heart 
rate (HR), body temperature, and O2 saturation.  
• Conduct full physical examination.  
• Obtain electrocardiogram (ECG; 12-lead).  

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 40 of 77 
 
• Collect blood samples for hematology, blood chemistry, coagulation, and viral testing, and 
urine sample for urinalysis. 
• Perform hemoglobin genotyping (for subjects with unknown genotype). 
• Conduct serum pregnancy test for women of childbearing potential (WOCBP). 
• Record concomitant medications (record all medications within 30 days of Visit 1).   
• Have subjects discontinue use of prohibited medications immediately after Visit 1 
(Screening). 
• Record adverse events. 
• Schedule Visit 2 (Day 1). 
6.1.2 
Visit 2; Randomization (Day 1) 
Randomization will be performed on Day 1. Participants will be in a fasted state.  There is no Day 
0 in this protocol.  The following assessments are to be completed prior to randomization: 
• Review Inclusion/Exclusion Review to ensure subject continues to qualify for the study. 
• Collect any adverse events since the Screening Visit. 
• Collect concomitant medication changes since the Screening Visit. Specifically collect 
opioid use since Screening. 
• Obtain vital sign measurements (BP, HR, body temperature, and O2 saturation.) 
• Conduct symptom-directed physical exam, as needed. 
• Obtain ECG (12-lead). 
• Collect blood samples for hematology and blood chemistry and urine for urinalysis. 
• Collect blood samples for CANs, CD62L, iFABP and LPS. 
• Collect urine sample for 3-indoxyl sulfate. 
• Confirm negative serum pregnancy test from Screening and conduct urine pregnancy test 
for WOCBP. 
• Query subject and record VOCs that have occurred since Screening. 
• If subject continues to meet eligibility requirement, randomize subject. 
After randomization, conduct the following assessments: 
• Collect pre-dose PK sample. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 41 of 77 
 
• Dispense study drug and instruct subject in administration (i.e., number of capsules to take 
[2 or 4] and timing of BID dosing). 
• Have subject administer first dose of study drug. 
• Collect PK blood samples at 0.5, 1, 1.5, 2, 3, 4, 5, and 8-hours post-dose.   
• Record any concomitant medications. 
• Record any adverse events. 
• Schedule Visit 3  
6.1.3 
Visit 3, (Day 8 ±1 day) and Visit 4, (Day 15 ±1 day) 
Participants will be in a fasted state.  The following assessments are to be completed at Visit 3 and 
Visit 4: 
• Collect any adverse events since Visit 2 or Visit 3. 
• Collect concomitant medication changes since Visit 2 or Visit 3. Specifically collect opioid 
use since Visit 2 or Visit 3. 
• Obtain vital sign measurements (BP, HR, body temperature, and O2 saturation.) 
• Conduct symptom-directed physical exam, as needed. 
• Collect blood samples for hematology and blood chemistry and urine for urinalysis. 
• Collect blood samples for CANs, CD62L, iFABP and LPS. 
• Collect urine sample for 3-indoxyl sulfate. 
• Query subject and record VOCs that have occurred since Visit 2 or Visit 3. 
• Collect unused study drug and review compliance and accountability.   
• Collect pre-dose PK sample. 
• Dispense study drug and confirm subject’s compliance with administration (i.e., number 
of capsules to take [2 or 4] and timing of BID dosing). 
• Have subject administer study drug, record AM or PM dose. 
• Collect PK blood samples at 0.5, 1, and 2-hours post-dose.     
• Record any concomitant medications. 
• Record any adverse events. 
• Schedule next Visit (Visit 4 or Visit 5). 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 42 of 77 
 
6.1.4 
Visit 5, (Day 29 ±1 day) EOT/ET Visit 
Participants will be in a fasted state.  The following assessments are to be completed at the EOT/ET 
Visit: 
• Collect any adverse events since Visit 4. 
• Collect concomitant medication changes since Visit 4. Specifically collect opioid use since 
Visit 4. 
• Obtain subject’s weight. 
• Obtain vital sign measurements (BP, HR, body temperature, and O2 saturation.) 
• Conduct symptom-directed physical exam, as needed. 
• Obtain ECG (12-lead). 
• Conduct urine pregnancy test for WOCBP. 
• Collect blood samples for hematology and blood chemistry and urine for urinalysis. 
• Collect blood samples for CANs, CD62L, iFABP and LPS. 
• Collect urine sample for 3-indoxyl sulfate. 
• Query subject and record VOCs that have occurred since Visit 4. 
• Collect pre-dose PK sample. 
• Collect unused study drug and review compliance and accountability.   
• Have subject administer final dose of study drug. 
• Collect PK blood samples at 0.5, 1, 1.5, 2, 3, 4, 5, and 8-hours post-dose.       
• Record any concomitant medications. 
• Schedule Visit 6.  
6.1.5 
Visit 6 (Day 30)  
• Obtain vital sign measurements (BP, HR, body temperature, and O2 saturation.) 
• Conduct symptom-directed physical exam, as needed 
• Record any concomitant medications. 
• Record any adverse events. 
• Collect PK blood sample at 24-hours post dose 
• Collect PK blood sample at 30-hours post dose 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 43 of 77 
 
6.1.6 
Visit 7 (Day 31) 
• Obtain vital sign measurements (BP, HR, body temperature, and O2 saturation.) 
• Conduct symptom-directed physical exam, as needed 
• Record any concomitant medications. 
• Record any adverse events. 
• Collect blood samples for CANs, CD62L, iFABP and LPS at 48-hours post dose. 
• Collect blood samples for hematology and blood chemistry  
• Collect urine sample for 3-indoxyl sulfate. 
• Collect PK blood sample at 48-hours post dose 
 
6.1.7 
Visit 8 (Day 32) 
• Obtain vital sign measurements (BP, HR, body temperature, and O2 saturation.) 
• Conduct symptom-directed physical exam, as needed 
• Record any concomitant medications. 
• Record any adverse events. 
• Collect PK blood sample at 72-hours post dose 
 
6.1.8 
Visit 9 (Day 43 ± 3 days) EOS Visit 
The following assessments are to be completed at the EOS Visit:  
• Collect any adverse events since Visit 8. 
• Collect concomitant medication changes since Visit 8. Specifically collect opioid use since 
Visit 8. 
• Obtain subject’s weight. 
• Obtain vital sign measurements (BP, HR, body temperature, and O2 saturation.) 
• Conduct symptom-directed physical exam, as needed. 
• Obtain ECG (12-lead) if abnormal findings were observed at Visit 5 (Day 29). 
• Conduct urine pregnancy test for WOCBP. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 44 of 77 
 
• Collect blood samples for hematology and blood chemistry and urine for urinalysis only if 
needed for follow-up of AEs or SAEs.   
• Collect blood samples for CANs, CD62L, iFABP and LPS. 
• Collect urine sample for 3-indoxyl sulfate 
• Query subject and record VOCs that have occurred since Visit 5. 
• Record any concomitant medications. 
• Record any adverse events. 
• Discharge subject from study.  Follow subject for AEs or SAEs as described in Section 7.7.  
 
6.1.9 
Visit to a Medical Facility for a VOC Event   
The following assessments are to be completed, when possible, when a subject visits a medical 
facility for treatment of a VOC:  
• Collect any adverse events since previous visit.  Do not record VOC events as an AE (See 
Section 7.3).   
• Collect concomitant medication changes since previous visit. Specifically collect opioid 
use. 
• Obtain vital sign measurements (BP, HR, body temperature, and O2 saturation). 
• Conduct symptom-directed physical exam. 
• Collect blood samples for hematology and blood chemistry and urine for urinalysis.   
• Collect blood samples for CANs, CD62L, iFABP and LPS. 
• Collect PK blood samples. 
• Collect urine sample for 3-inoxyl sulfate. 
6.1.10 
Unscheduled Visit 
The Investigator may perform an unscheduled visit at any time during the study at his/her 
discretion.  Assessments performed at an unscheduled visit should be symptom directed.   
The following procedures must be performed at all unscheduled visits: 
• Collect and record hospital admission and death data. 
• Safety laboratory testing.  Repeat laboratory testing may be needed based on results from 
the unscheduled laboratory testing. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 45 of 77 
 
• Concomitant medications 
• Adverse events 
If the subject is discontinued from the study at an unscheduled visit, the visit will be considered 
Visit 9 (EOT) and all of the EOT assessments should be completed.   
6.2 
Outcome Assessments 
Endpoints are presented in Section 2.2.  Analyses are described in Section 8.0.  
The following assessments will be utilized throughout the study.   
6.2.1 
Assessment of Pharmacokinetics 
Blood samples for analysis of plasma rifaximin and 25-desacetyl rifaximin pharmacokinetics will 
be collected as described in Appendix 2.  Full PK assessments through 8-hour and 72-hours post 
dose will be performed at Visit 2 (Day 1) and Visits 5 to 8 (Days 29 to 32), respectively.  Samples 
will be obtained pre-dose and at 0.5, 1, 1.5, 2, 3, 4, 5, and 8-hours post-dose on Days 1 and 29.      
At Visit 3 (Day 8) and Visit 4 (Day 15) samples will be obtained pre-dose and at 0.5, 1, and 2-hours 
post-dose. 
Additionally, post-final dose assessments will be done on: 
Visit 6: 24 and 30 hours post-final dose 
Visit 7: 48 hours post-final dose 
Visit 8: 72 hours post-final dose. 
The windows around the collection timepoints are:  
• within 15 minutes prior to dose for pre-dose samples,  
• ± 5 minutes for samples taken at 0.5 hours through 1.5 hours, and  
• ±10 minutes for samples taken 2 hours through 8 hours. 
• 
±2 hours for samples taken 24 hours through 72 hours. 
In addition, when possible, a sample will be obtained for PK assessment during a medical facility 
visit for a VOC.  The time of the last dose of study drug will be recorded. 
If the subject is to begin treatment with a P-gp inhibitor, a plasma sample for PK analysis should 
be collected during treatment with both rifaximin and the P-gp inhibitor. This sample should be 
collected at the next scheduled visit, if possible. Alternately, an unscheduled PK sampling visit 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 46 of 77 
 
should occur. The date and time of the last 2 rifaximin doses, as well as the last 2 doses of the P-
gp inhibitor should be recorded. 
Study participants should be instructed to take the study drug on an empty stomach. The morning 
(AM) dose should be taken on an empty stomach, and subjects must avoid food for two hours after 
taking the study drug. The evening (PM) dose should be taken on an empty stomach (at least two 
hours after the last meal), and subjects must avoid food for two hours after taking the study drug.  
On Days 1, 8, 15, and 29, Participants will fast for a minimum of 10 hours prior to, and 2 hours 
after, the morning study drug administration. Water will be restricted from one hour prior to dosing 
through one hour following dosing, except for the water that will be consumed at dosing. 
6.2.2 
Assessments of Pharmacodynamics 
The pharmacodynamics of rifaximin ER and DER will be assessed through collection of ANC, 
CANs, serum CD62L, hsCRP, the gut permeability biomarkers serum iFABP and LPS, and the 
gut bacteria biomarkers urine 3-indoxyl sulfate according to the schedule in Appendix 1.  These 
assessments will be conducted at a central laboratory.  Instructions for collection, preparation, 
storage, and shipment of samples will be provided in the Laboratory Manual.   
6.2.3 
Assessment of Safety 
Safety endpoints are presented in Section 2.2.2.  Safety will be assessed throughout the duration 
of the study.    
Safety assessments will include the following: 
• Adverse events (AEs),  
• Vital signs (systolic and diastolic blood pressure, heart rate, oral body temperature, and 
oxygen saturation),  
• Clinical safety laboratory tests,  
• Physical exams (PEs), and  
• Electrocardiograms (ECGs).   
6.2.3.1 
Clinical Laboratory Tests 
Clinical laboratory tests to be performed during the study are outlined in Table 2.  The samples 
will be analyzed by a central clinical laboratory. Exceptions may be made as necessary for local 
laboratory testing.  At the Investigator’s discretion, additional blood may be collected for clinical 
laboratory tests.  Results from laboratory specimens collected during Screening must be received 
by the site prior to Visit 2.  
 
Note: CANs assay examiners will be trained and certified on CANs assessment requirements using flow 
cytometry prior to screening patients (conducted on separate, healthy volunteers). 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 47 of 77 
 
 
It is the responsibility of the Investigator to assess the clinical significance of all abnormal clinical 
laboratory values as defined by the list of normal values on file for the central laboratory. All 
clinically significant laboratory value abnormalities are to be recorded as AEs. 
A clinically significant laboratory value is any abnormal result that, in the judgment of the 
Investigator, is an unexpected or unexplained laboratory value or if medical intervention or 
corrective action (transfusion, hydration, initiation of antibiotics or other concomitant medication) 
is required. Any abnormal values that persist should be followed at the discretion of the 
Investigator.  Additional and repeat laboratory safety testing for the evaluation of abnormal results 
and/or AEs during the study may be performed at the discretion of the Investigator or upon request 
of the Sponsor.  Repeat laboratory testing of abnormal potentially clinically significant or clinically 
significant results for the Screening evaluation of the subject may be repeated once at the discretion 
of the Investigator. 
Tests listed in Table 2 will be performed as outlined in the Schedule of Assessments (Appendix 1). 
Details on collection, preparation, and shipping of blood samples are provided in the Laboratory 
Manual. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 48 of 77 
 
Table 2.   Clinical Laboratory Tests 
Hematology 
• Hemoglobin 
• Hematocrit  
• White blood count and differential 
• Red blood cell count 
• Percent and absolute reticulocyte count 
• Platelet count 
 
 
 
Coagulation 
• Prothrombin time 
• INR 
Serum Chemistry 
• Blood Urea Nitrogen 
• Bilirubin (total, direct, and indirect) 
• Alkaline phosphatase 
• Aspartate aminotransferase 
• Alanine aminotransferase 
• Albumin 
• Sodium 
• Potassium 
• Magnesium 
• Calcium 
• Chloride 
• Bicarbonate  
• Glucose 
• Creatine kinase 
• Creatinine 
• Lactate dehydrogenase 
• High sensitivity C-Reactive protein (hs-
CRP) 
• Total globulin 
• Total protein 
• Lipid Panel 
- 
Total cholesterol 
- 
HDL 
- 
LDL  
- 
Triglycerides 
Additional Tests 
• Hemoglobin genotype (if not previously 
determined) using HPLC/electrophoresis 
• Serum pregnancy test (WOCBP only)* 
• Urine pregnancy test (WOCBP only) 
 
 
* WOCBP, women of child-bearing potential 
 
6.2.3.2 
Pregnancy Tests 
A pregnancy test will be performed for all women of childbearing potential according to the 
schedule in Appendix 1.  A negative serum pregnancy test performed at Screening must be 
confirmed along with a negative urine pregnancy test on Day 1 prior to randomization and 
dispensing/administration of study drug.    
6.2.3.3 
Adverse Events 
The Investigator is responsible for the detection and documentation of events that meet the 
definition of an AE or SAE as provided in this protocol.  Assessments of occurrences of AEs or 
SAEs should be conducted during each study visit or as reported by the subject outside of 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 49 of 77 
 
scheduled visits. To fulfill safety reporting obligations, the Investigator should include in his or 
her assessment any AEs resulting from study participation regardless of relation to study drug (e.g., 
complications resulting from the taking of a blood sample). 
6.2.3.4 
Vital Signs 
Vital signs will include blood pressure (systolic and diastolic in mm Hg), heart rate (beats per 
minute), body temperature, and O2 saturation.  Vital sign measurements will be collected at every 
visit.  Subjects should be seated for 5 minutes prior to assessment of vital signs.  Blood pressure 
measurements should be measured on the same arm throughout the study.   
6.2.3.5 
Electrocardiogram (ECG) 
A 12-lead ECG (Supine) will be performed on all subjects using a standard ECG machine at 
Visit 1, (Screening), Visit 2 (Baseline), Visit 5 (Day 29/EOT/ET), and Visit 9 (Day 43/EOS), if 
applicable.  
6.2.3.6 
Physical Examination 
A full physical examination will be performed at Visit 1 (Screening).  Symptom-directed physical 
examinations will be performed at other visits.  Weight will be collected as outlined in Appendix 1.  
Height will only be collected at Visit 1 (Screening). 
6.3 
Other Assessments 
6.3.1 
Assessment of VOCs 
VOCs that subjects experience during the study will be collected.  A VOC is defined as:  
o The occurrence of appropriate symptoms consistent with a painful crisis, acute 
chest syndrome (ACS), or priapism, and  
o Requires visit to a medical facility, and 
o Receipt of either a parenteral or oral opioid or NSAID analgesia. 
For each VOC, the information outlined in Section 7.3 will be collected.   
6.3.2 
Medical History 
Each subject’s complete medical history is to be recorded in source documents and the appropriate 
eCRF pages.  Relevant medical history will be collected for the 3 months prior to the Screening 
Visit.  A detailed history of the subject’s VOCs over the past 12 months will be obtained and will 
include the start and stop dates (if known), the treatment setting, and treatment including drug, 
dose, route of administration, and duration of treatment for each VOC, when possible. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 50 of 77 
 
7.0 
SAFETY REPORTING 
7.1 
Operating Definitions for Assessing Safety 
Safety data collection for this study begins at the time of the subject’s signing of the informed 
consent according to the operating definitions defined in this section of the protocol.  The 
Investigator is responsible for the detection and documentation of events that meet the definition 
of an AE (Section 7.1.1), or SAE (Section 7.1.2). 
7.1.1 
Adverse Event 
An adverse event is any untoward medical occurrence in a clinical investigation subject 
administered a study product and which does not necessarily have to have a causal relationship 
with this treatment. 
An AE can therefore be any unfavorable and unintended sign (that could include a clinically 
significant abnormal laboratory finding), symptom, or disease temporally associated with the use 
of a study product, without any judgment about causality (i.e., whether or not considered related 
to the study product). 
An AE does include the following: 
• Exacerbation or worsening of a pre-existing illness including symptoms associated with 
SCD. 
• Condition detected or diagnosed after study product administration even though it may 
have been present prior to the start of the study. 
An AE does not include the following: 
• Medical or surgical procedures (e.g., surgery, endoscopy, tooth extraction, transfusion) as 
event terms; the condition that led to the procedure is the AE if it meets the definition of 
an AE. 
• Situations where an untoward medical occurrence has not occurred (e.g., hospitalization 
for cosmetic elective surgery; and social and/or convenience admissions).  
• Symptoms associated with disease, which are consistent with the subject’s usual clinical 
course; unless the subject experiences worsening of their symptom(s) or the symptom(s) 
meet the criteria for an SAE (exception is VOC and presenting symptoms, Section 7.3). 
7.1.2 
Serious Adverse Event 
A serious adverse event is any untoward medical occurrence that, at any dose:  
• Results in death, 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 51 of 77 
 
• Is life-threatening. 
NOTE:  The term “life-threatening” in the definition of “serious” refers to an event in 
which the subject was, in the view of the Investigator or Sponsor, at risk of death at the 
time of the event.  It does not refer to an event which hypothetically might have caused 
death if it were more severe.    
• Requires inpatient hospitalization or prolongation of existing hospitalization. 
NOTE: Complications that occur during hospitalization are AEs. If a complication 
prolongs hospitalization or fulfills any other serious criteria, the event is serious. 
Hospitalization for elective treatment of a pre-existing condition that did not worsen from 
Baseline is not considered to be an AE.  “In-patient” hospitalization means the subject has 
been formally admitted to a hospital for medical reasons for 24 hours or more.  It does not 
include presentation at a casualty or emergency room. 
• Results in a persistent or significant incapacity or substantial disruption of the ability to 
conduct normal life functions. 
NOTE: The term disability means a substantial disruption of a person’s ability to conduct 
normal life functions. This definition is not intended to include experiences of relatively 
minor medical significance such as uncomplicated headache, nausea, vomiting, diarrhea, 
influenza, or accidental trauma (e.g., sprained ankle) that may interfere or prevent everyday 
life functions but do not constitute a substantial disruption. 
• Is a congenital anomaly or birth defect in the offspring of a subject who received study 
product. 
Important medical events that do not result in death, are not life-threatening, and/or do not require 
hospitalization may be considered an SAE when, based upon appropriate medical judgment, they 
may jeopardize the subject or may require medical or surgical intervention to prevent one of the 
outcomes listed in this definition.   
NOTE: Examples of such medical events include allergic bronchospasm requiring intensive 
treatment in an emergency room or at home, blood dyscrasias or convulsions that do not result 
in inpatient hospitalization, or the development of drug dependency or drug abuse. 
Additionally, an adverse event meeting any of the serious outcomes previously defined above that 
is assessed by the Investigator as resulting from study participation (regardless of relationship to 
study drug) should be treated as an SAE for this protocol (e.g., complications resulting from the 
taking of a blood sample or performance of a protocol required procedure).   
Medical and scientific judgment should be exercised in deciding whether expedited reporting is 
appropriate in case of events that do not meet the serious criteria. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 52 of 77 
 
If a subject has an SAE, a plasma sample for PK analysis will be collected as soon as feasible, and 
the date and time of the last 2 rifaximin doses will be recorded.  
7.2 
Clinical Laboratory Abnormalities and Other Abnormal Assessments as AEs 
and SAEs 
Abnormal laboratory findings (e.g., clinical chemistry, hematology) or other abnormal 
assessments (e.g., abnormal findings during examinations, the taking of vital signs, or ECG 
monitoring) that are judged by the Investigator as clinically significant must be recorded as AEs 
or SAEs if they meet the definition of an AE or SAE.  The Investigator should exercise his or her 
medical and scientific judgment in deciding whether an abnormal laboratory finding or other 
abnormal assessment (including ECG monitoring) is clinically significant.  Abnormal laboratory 
findings consistent with pre-existing illness or confirmatory of a reported AE or SAE should not 
be reported as a separate AE or SAE.  If a clinically significant change from Baseline is observed 
which is indictive of worsening in condition, then the worsening condition should be reported as 
the AE or SAE. 
7.3 
Adverse Events That Are VOC Endpoint Events 
VOC events that are listed in Table 3 are being captured as endpoints and SHOULD NOT be 
reported as an AE or SAE for purposes of this study.  These events will not be considered as 
SAEs for reporting requirements. 
 
Table 3: VOC Events Not Requiring AE/SAE Reporting 
Uncomplicated pain crisis* 
Acute chest syndrome 
Hepatic sequestration 
Splenic sequestration 
Priapism requiring a visit to a medical facility 
* Defined as the occurrence of appropriate symptoms, results in a visit to a medical facility and or 
healthcare professional and requires either parenteral or oral opioid or NSAID analgesia, but is NOT 
classified as an acute chest syndrome, hepatic sequestration, splenic sequestration, or priapism. 
 
All VOCs are to be recorded only once on the “Vaso-Occlusive Event” eCRF page. All VOCs are 
to be recorded throughout the entire treatment period, up to Visit 5 (Day 29), and should continue 
until the Follow-Up Visit at Day 43.  The Investigator will classify and provide all the following 
information for each VOC as follows: 
• Diagnosis, which will be limited to one of the five pre-defined VOC events as: 
o Uncomplicated pain crisis 
o ACS 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 53 of 77 
 
o Hepatic sequestration 
o Splenic sequestration 
o Priapism (requiring a visit to a medical facility) 
• Onset date, 
• Stop date, 
• Action taken (None, Required concomitant medication, Temporarily withheld study drug, 
Permanent discontinuation of study drug, or Other [explain]), 
• Treatment setting, 
• Concomitant medications given, and 
• Outcome (Recovered without sequelae, Resolved with sequelae, Ongoing, Unknown, 
Death). 
If a subject is hospitalized due to a VOC and during hospitalization develops a non-VOC event 
that meets the criteria for a SAE, then that event should be reported as a SAE. Any prolongation 
of a hospitalization due to a non-VOC event (even though they may have initially been hospitalized 
due to a VOC) is reportable as a SAE in the eCRF. 
7.4 
Method, Frequency, and Time Period for Detecting AEs and SAEs 
At each assessment, after the subject has had an opportunity to spontaneously mention any 
problems, the Investigator should inquire about AEs by asking the following questions: 
1. Have there been any (other) medical problems since your last visit/assessment?” 
2. Have any new medications been taken, other than those given to you in this study, since 
your last visit/assessment?” 
7.4.1 
Time Period for Detecting and Reporting of AEs and SAEs 
The time period for detecting and reporting AEs and SAEs is from the time of informed consent 
through study completion/withdrawal, including the follow-up period.  
7.4.2 
Post-Study SAEs 
Investigators are not obligated to actively seek SAE information in former study subjects, but 
Investigators are encouraged to notify the Sponsor/designee of any SAEs occurring at any time 
after a subject has discontinued or terminated study participation that they judge may reasonably 
be related to study treatment or study participation.   
7.5 
Documenting AEs and SAEs 
All AEs that occur after the subject has signed the ICF through 28 days after last dose of study 
medication, regardless of causality or seriousness, will be assessed and recorded in the subject’s 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 54 of 77 
 
source documents and in the eCRF. If a subject is withdrawn during treatment, they must be 
followed for 28 days after the last dose as well. In addition, SAEs must be documented on the 
paper SAE Report Form.  
The Investigator should attempt to establish a diagnosis for the event based on signs, symptoms, 
and/or other clinical information.  In such cases, the diagnosis should be documented as the AE or 
SAE and not the individual signs/symptoms.  When this is not possible, the AE should be 
documented in terms of signs and/or symptoms observed by the Investigator or reported by the 
subject at each study visit. Each AE which appears to be independent of any prior event will be 
reported separately. 
For clinically significant abnormal laboratory findings or other abnormal assessments meeting the 
definition of an AE or SAE, a diagnosis, if known (or clinical signs and symptoms if a diagnosis 
is unknown), should be recorded by the Investigator. If a diagnosis is unknown and clinical signs 
and symptoms are not present, then the abnormal finding should be recorded. When documenting 
as an SAE on the SAE Report Form, relevant laboratory (including the reference range and units) 
or copies of the laboratory report (with reference ranges and units) should be sent with the SAE 
Report Form. 
The SAE Report Form should be completed as thoroughly as possible and signed by the 
Investigator or his/her designee before transmittal to the Sponsor/designee.  Investigators should 
not wait to receive additional information to fully document the event before notifying the Sponsor 
of an SAE.  It is very important that the Investigator (or designee) provide his/her assessment of 
causality to study product at the time of initial SAE reporting. 
7.6 
Common Terminology Criteria for Adverse Events 
The severity of events will be determined based on the Common Toxicity Criteria for Adverse 
Events CTCAE), version 5.0. The CTCAE quick reference guide can be found at: 
https://ctep.cancer.gov/protocolDevelopment/electronic_applications/docs/CTCAE_v5_Quick_R
eference_8.5x11.pdf 
For events not specifically addressed in the CTCAE, the following definitions should be 
considered when evaluating the severity of AEs and SAEs: 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 55 of 77 
 
Severity of Event 
Grade 1 
Mild; asymptomatic or mild symptoms; clinical or diagnostic observations 
only; intervention not indicated. 
Grade 2 
Moderate; minimal, local or noninvasive intervention indicated; limiting 
age-appropriate instrumental ADL*. 
Grade 3 
Severe or medically significant but not immediately life-threatening; 
hospitalization or prolongation of hospitalization indicated; disabling; 
limiting self-care ADL**. 
Grade 4 
Life-threatening consequences; urgent intervention indicated. 
Grade 5 
Death related to AE. 
Activities of Daily Living (ADL)  
* 
Instrumental ADL refer to preparing meals, shopping for groceries or clothes, using 
the telephone, managing money, etc.  
** Self-care ADL refer to bathing, dressing and undressing, feeding self, using the toilet, 
taking medications, and not bedridden. 
 
7.7 
Assessment of Causality  
The Investigator should assess the relationship of the AE, if any, to the study drug as either 
“Related” or “Not Related.”   
• Related:  There is at least a reasonable possibility that the AE/SAE is related to the study 
drug.  Reasonable possibility means that there is evidence to suggest a causal relationship 
between the drug and the AE. 
• Not Related:  There is little or no reasonable possibility that the AE/SAE is related to the 
study drug.  This assessment implies that the AE/SAE has little or no temporal relationship 
to the study drug and/or a more likely or certain alternative etiology exists. 
The following should be considered when assessing AE/SAE causality: 
• Positive temporal relationship to study drug, such as if study drug was withdrawn and the 
SAE resolved, or the event recurred after re-introduction, 
• If there is a reasonable possibility that the AE is associated with an underlying or 
concomitant illness. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 56 of 77 
 
• Possible association with previous or concomitant therapy, 
• No temporal relationship to treatment with study drug and/or a more likely alternative 
etiology exists. 
• If the AE is directly related to study procedures. 
7.8 
Follow-up of AEs and SAEs 
All AEs, regardless of seriousness, must be followed until resolution, until the condition stabilizes, 
until the event is otherwise explained, or until the subject is lost to follow-up.  The Investigator is 
responsible for ensuring that follow-up includes any supplemental investigations as may be 
indicated to elucidate as completely as practical the nature and/or causality of the AE.  This may 
include additional laboratory tests or investigations, histopathological examinations, relevant 
hospital records (i.e., discharge summary), or consultation with other health care professionals. 
Salix may request that the Investigator perform or arrange for the conduct of supplemental 
measurements and/or evaluations.  If a subject dies during participation in the study or during 
follow-up period, the Sponsor/designee should be provided with a copy of any postmortem 
findings, including histopathology. 
If cause of death is not available within the 24-hour reporting period, “death” must be reported as 
SAE term to meet timelines and the cause of death actively queried and submitted as a follow-up 
report. 
When additional SAE information becomes available, it should be recorded on a new SAE Report 
Form and should be labeled as a “Follow-up Report”.  The original SAE Report Form should not 
be altered.  All completed SAE Report Forms must be signed and dated by the Investigator or 
designee. By signing the SAE Report Form, the Investigator or designee attests to the accuracy 
and completeness of the data and that he/she has reviewed and approved the report being 
submitted.  The investigational sites IRB/EC must be notified about SAEs in accordance with the 
requirements of the governing IRB/EC.  
Patients should be monitored for development of Clostridium difficile-associated diarrhea 
(CDAD). If a patient develops severe, unremitting diarrhea, a diagnosis of Clostridium difficile-
associated diarrhea (CDAC) should be considered and investigated. If CDAD is confirmed during 
the study, the interventional therapy will be stopped, and the subject will be discontinued from the 
trial. Symptoms of CDAD may be non-specific and indistinguishable from other causes of 
diarrhea, but if CDAD is suspected, study drug must be held until CDAD can be ruled out. If 
CDAD is confirmed, then the interventional therapy will be stopped, and the subject will be 
discontinued from the trial. CDAD must also be reported as an AE or SAE depending on 
presentation. Appropriate fluid and electrolyte management, protein supplementation, antibiotic 
treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated. 
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 57 of 77 
 
7.9 
Prompt Reporting of SAEs to Salix Pharmaceuticals, Inc. 
SAEs must be reported promptly to the Sponsor/designee once the Investigator determines that the 
event meets the protocol definition of a SAE. 
Prompt reporting of an SAE requires: 
• Completion and transmission of the SAE Report Form to the Sponsor/designee via email or 
fax within 24 hours of the Investigator’s knowledge of the event.  In parallel, a corresponding 
AE with the SAE details should be entered into the AE eCRF within 48 hours of submitting 
the paper SAE Report Form.   
• Prompt reporting of additional information for previously reported SAEs should follow the 
same reporting timeframe as initial reports. In addition, the corresponding AE in the AE eCRF 
(as applicable) should be updated to ensure all data points documented in the AE eCRF are 
aligned with the matching data points on the paper SAE Report Form. 
7.10 
Pregnancy Reporting 
Pregnancies detected in subjects assigned to study treatment should be promptly reported to the 
Sponsor/designee via email/fax, using the Pregnancy Report Form, as soon as the Investigator is 
notified.  If a female subject becomes pregnant following assignment to study treatment, the study 
drug will be immediately discontinued, and the subject will be followed until the outcome of the 
pregnancy is known. (Refer to the Section 4.4).   
The Sponsor/designee should be notified via email/fax of any updates on the status of the 
pregnancy within 24 hours by completion of a separate follow-up pregnancy notification form.  
Outcome of pregnancy must be reported.  
Although pregnancy occurring in a clinical study is not considered to be an AE or SAE, any 
pregnancy complication or elective termination of a pregnancy will be recorded as an AE or SAE 
and followed as such.  If a pregnancy is associated with an SAE, an SAE Report Form should be 
forwarded to the Sponsor/designee within 24 hours of the Investigator’s awareness, along with the 
Pregnancy Report Form.  
7.11 
Transmission of SAE Report Forms and Pregnancy Report Forms 
Completed SAE Report Forms and completed Pregnancy Report Forms should be transmitted to 
the Sponsor/designee via the email address provided below:  
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 58 of 77 
 
7.12 
Contraception Requirements 
All women of childbearing (reproductive) potential and all men must practice effective 
contraception during the study and for 30 days after the last dose. 
For the purposes of this study, women who do not meet one of the following criteria listed below 
are considered physiologically capable of becoming pregnant and are, therefore, defined as women 
of childbearing potential: 
• Postmenopausal 
• 24 months of natural (spontaneous) amenorrhea without an alternative medical cause  
• 6 weeks after surgical bilateral oophorectomy with or without hysterectomy 
• Post-hysterectomy 
• Female surgical sterilization (e.g., bilateral tubal ligation) 
For the purposes of the study, effective contraception is defined as use of 2 of the following for 
females: 
• Oral contraceptives taken for at least 30 days prior to the Screening Visit and maintain 
contraceptive regimen throughout the study. 
• Placement of a non-hormonal intrauterine device or intrauterine system. 
• Barrier methods of contraception with use of a spermicide: condom or occlusive cap 
(diaphragm or cervical/vault caps) with spermicidal foam/gel/film/cream suppository. The 
use of barrier contraceptives should always be supplemented with the use of a spermicide. 
• Male surgical sterilization (with the appropriate post-vasectomy documentation of the 
absence of sperm in the ejaculate). 
For the purposes of the study, effective contraception is defined as use of 1 of the following for 
males: 
• Effective male contraception includes a vasectomy with negative semen analysis at 
follow-up. 
• The use of condoms with spermicide. 
• Confirmation of birth control practiced by female partner with condom use. 
True abstinence, when this is consistent with the preferred and usual lifestyle of the subject, can 
be considered an acceptable method of contraception based on the evaluation of the Investigator, 
who should also take into consideration the duration of the clinical trial.  Periodic abstinence (e.g., 
calendar, ovulation, symptothermal, postovulation methods) and withdrawal are not considered 
acceptable methods of contraception. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 59 of 77 
 
8.0 
STATISTICAL CONSIDERATIONS 
Detailed methodology for statistical analyses of the data collected in this study will be documented 
in a Statistical Analysis Plan (SAP).  The SAP will be finalized prior to database lock. 
All continuous variables will be summarized using descriptive statistics; N, mean, standard 
deviation (SD), median, maximum, and minimum. All categorical variables will be summarized 
using frequency counts and percentages. 
Baseline value is defined as last available value prior to the first dose of study drug. 
EOT value is defined as last available post-Baseline value during the treatment period. 
All data collected in the database will be presented in data listings. 
8.1 
Randomization 
Subjects who meet the eligibility criteria and have given written informed consent will be 
randomized in a 2:2:1:2:2:1 allocation to one of six treatment groups as noted in Section 3.2. 
8.2 
Sample Size 
The total of 60 subjects is not based on formal statistical considerations.  Twelve (12) subjects per 
group receiving active rifaximin is considered adequate to evaluate the PK/PD of rifaximin ER 
and DER.   
8.3 
Analysis Populations 
 The analysis populations will be defined as follows: 
• Safety Population will include all subjects who have taken at least one dose of study 
drug.    
• PK Population will include all subjects who have taken at least one dose of study drug 
and have sufficient data to calculate PK parameters for rifaximin and 25-desacetyl 
rifaximin. 
Summarization of disposition, demography and Baseline characteristics, PD assessments, VOCs, 
and safety will be performed using the Safety Population.  PK analyses will be conducted using 
the PK Population.  
8.4 
Analysis Methods 
8.4.1 
Methods of Analysis 
All statistical procedures and non-compartmental analyses (NCA) will be completed using SAS® 
version 9.4 or higher or WinNonlin v8.1, respectively, or more recent versions of either program. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 60 of 77 
 
The placebo arms will be combined for all descriptive summaries of subject disposition, 
demography and Baseline characteristics, PD, VOCs, and safety. 
8.4.2 
Subject Disposition 
Subject disposition will be summarized for all randomized subjects, by dose (40 mg BID or 80 mg 
BID) within formulation (ER or DER), and combined placebo and will include the number of 
subjects randomized; number and percentage of subjects who completed or prematurely 
discontinued the study, classified by reasons for premature discontinuation; the number of subjects 
randomized at each study site; and the number and percentage of subjects who completed or 
discontinued the study at each study site. 
8.4.3 
Demographics and Baseline Characteristics 
Age, gender, race, ethnicity, height, and weight will be summarized for the entire population, by 
dose within formulation and combined placebo.  Baseline characteristics will include number of 
VOCs in the previous year, concurrent treatment with HU, use of IOA and orally administered 
opioids (in morphine milligram equivalents [MME]), and SCD genotype. 
8.4.4 
Pharmacokinetics  
Concentrations of rifaximin and its metabolite (25-desacetyl rifaximin) will be summarized by 
formulation and by dose.  Concentrations will be summarized for samples taken for 8 and 72 
hours after the initial dose and the final dose, respectively.   
Dense sampling for initial dose (first dose interval): Cmax, Tmax, AUClast, AUC0-8h, and MR_AUC0-
8h,  will be summarized. 
Dense sampling for final dose: Cmax, Tmax, Cmin, Cavg, AUC0-8h, CL/Fss, Vz/Fss, RCmax, RAUCτ, 
AUClast, AUCinf, λz, t1/2, and MR_AUC0-8h, will be summarized.   
Steady state levels will be summarized for all subjects based on Ctrough on Day 8, Day 15, and 
Day 29. 
Additional PK parameters maybe calculated if it deemed necessary.  
 
 
 LIST OF PHARMACOKINETIC TERMS  
Parameter  Definition  
AUClast Area under the plasma drug concentration-time curve from time 0 to the last 
quantifiable drug concentration  
AUCinf Area under the plasma drug concentration-time curve from time 0 extrapolated to 
infinity  

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 61 of 77 
 
AUC0-8h Area under the plasma drug concentration-time curve from time 0 through 8 hours  
Cavg Average plasma concentration at steady-state  
Cmax Maximum observed plasma concentration  
Cmin Minimum observed plasma concentration  
Ctrough Observed plasma concentration at the end of a dosing interval, just prior to the 
administration of the next dose  
Tmax Time of maximum observed plasma concentration  
t1/2 Apparent terminal elimination half-life  
λz Terminal elimination rate constant  
CL/Fss Apparent systemic extravascular clearance at steady-state  
Vz/Fss Apparent extravascular volume of distribution during the terminal elimination phase 
at steady-state  
RAUC Accumulation ratio of AUCτ at steady-state to AUClast after the first dose  
RCmax Accumulation ratio of Cmax at steady-state to Cmax after the first dose  
MR_AUC Metabolite-to-parent ratio for AUC  
 
8.4.5 
Pharmacodynamics 
The changes from Baseline in ANC, the number of CANs, and the levels of serum CD62L, serum 
iFABP, serum LPS, serum hsCRP, and urine 3-indoxyl sulfate will be summarized by dose within 
formulation and combined placebo. 
A dose-response analysis may be conducted to determine the relationship between daily rifaximin 
ER and DER dosing and reduction of CANs. Dose-response relationships following the final dose 
on Day 29 may also be assessed for other PD endpoints, if warranted.  
The relationship between rifaximin PK parameters (Ctrough, Cmax,ss, Css,avg) and each PD endpoint 
(ANC, CANs, serum CD62L levels, serum hsCRP, serum iFABP, serum LPS and urine 3-inoxyl 
sulfate) may be evaluated following the final dose on Day 29.  Additionally, a population PK/PD 
model may be developed as a separate analysis to explore exposure-response.  If conducted, this 
analysis will be reported separately from the Clinical Study Report. 
 
8.4.6 
Analysis of Safety 
All adverse events occurring during the study will be recorded and classified based on MedDRA 
terminology.  Only adverse events that occur after the start of study drug, (treatment emergent 
adverse events [TEAEs]); all AEs will be included in by-subject listings.   
TEAEs will be summarized for the entire population, by dose within formulation and combined 
placebo, and by severity and relationship to study medication.  Each subject will be counted only 
once within a system organ class or a preferred term by using the adverse event with the highest 
severity or greatest relationship, respectively, within each category. 
Treatment-emergent AEs will be summarized as follows: 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 62 of 77 
 
• Number and percentage of subjects experiencing TEAEs, 
• Number and percentage of TEAEs by relationship to study treatment (i.e., related or 
unrelated), 
• Number and percentage of TEAEs by severity, 
• Number and percentage of subjects experiencing serious AEs (SAEs), 
• Number and percentage of subjects experiencing study drug-related SAEs, 
• TEAE leading to permanent treatment discontinuation, 
• TEAEs with an outcome of death. 
All SAEs, AEs leading to premature withdrawal from the study, and all deaths, will be listed. 
Reports of diarrhea due to C. difficile will be summarized.  
Vital signs will include supine blood pressure (mmHg), heart rate (beats per minute), body 
temperature, and O2 saturation.  Vital signs will be summarized at Baseline and for each day when 
vital signs were obtained.  Changes from Baseline in vital sign measurements will also be 
summarized.  For each summary the N, mean, median, SD, minimum, and maximum values will 
be given for all subjects, by dose within formulation and combined placebo.  Pretreatment vital 
signs obtained closest in time to first dose of study drug will be used for summarization and 
analysis of Baseline and change from Baseline vital signs. 
Changes from Baseline in abbreviated physical exam findings of clinical significance will be 
summarized and listed.   
8.4.7 
Clinical Safety Laboratory Findings 
Clinical safety laboratory data (hematology, chemistry, and urinalysis) will be summarized at 
Baseline and at each visit per the schedule of assessments, as well as changes from Baseline in 
laboratory parameters.  For each summary the N, mean, median, SD, minimum, and maximum 
values will be given by dose within formulation and combined placebo.  Pretreatment laboratory 
values obtained closest in time to first dose of study drug will be used for summarization of 
Baseline and change from Baseline.  Pregnancy testing results (urine and serum) will be presented 
in by-subject listings. 
Clinical safety laboratory tests performed during the study will be primarily analyzed by a central 
clinical laboratory. 
8.4.8 
ECG Findings 
ECGs with abnormal findings will be summarized and listed.   

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 63 of 77 
 
8.4.9 
Physical Examinations 
Abnormal findings from full and symptom-directed physical examinations will be summarized 
and listed.  
8.4.10 
Protocol Deviations 
Protocol deviations will be presented in a listing. 
8.4.11 
Treatment Compliance 
Treatment compliance, based upon expected number of capsules to be used and actual number of 
capsules used, will be calculated and summarized. 
8.4.12 
Treatment Exposure 
The total exposure to study drug will be calculated for each subject.  
8.4.13 
Missing Data 
Only available data will be analyzed.  There will be no imputation of missing data. 
8.5 
Statistical and Analytical Issues 
8.5.1 
Adjustment for Covariates 
Not applicable.   
8.5.2 
Interim Analyses and Data Monitoring  
Not applicable. 
8.5.3 
Multicenter Study 
Statistical analyses of efficacy and safety parameters will be based upon pooled data from all study 
centers.   
8.5.4 
Noncompartmental Analysis of Rifaximin and 25-desacetyl rifaximin 
NCA will be conducted for subjects using intensive PK samples collected at Visit 2 (Day 1) and 
Visits 5 to 8 (Days 29 to 32).  PK parameters listed in Section 8.4.4 will be summarized using 
descriptive statistics, including number of observations, mean, median, CV%, SD, minimum, and 
maximum. 
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 64 of 77 
 
9.0 
STUDY ADMINISTRATION 
9.1 
Investigator Information and Training 
The Investigators and essential support staff will be trained by Salix or designee on Good Clinical 
Practices (GCPs) and all aspects of protocol application and study management.  It is the responsibility of 
the Investigator to ensure training of ancillary study staff. CANs assay examiners will be trained and 
certified on CANs assessment requirements using flow cytometry prior to screening patients (using 
healthy volunteers). 
 
9.2 
Monitoring 
This study will be monitored by Salix or designee, in accordance with GCPs and applicable 
regulations.  By signing this protocol, the Investigator agrees to periodic, on-site monitoring of all 
appropriate study documentation. 
The progress of the study will be monitored by periodic on-site visits and frequent communications 
between the Sponsor or designee(s) and the Investigator (either by phone, fax, email, or post). 
During these contacts, the monitor will: 
• check and assess the progress of the study; 
• review study data collected; 
• conduct source document verification; and 
• identify any issues and address their resolution. 
The objectives of monitoring procedures are to verify that data are authentic, accurate, and 
complete; that the safety and rights of subjects are being protected; and that the study is conducted 
in accordance with the currently approved protocol (and any amendments), GCPs, and all 
applicable regulatory requirements. 
9.3 
Audits 
At its discretion, Salix, or its designee, may conduct a quality assurance audit of this study.  If such 
an audit occurs, the Investigator agrees to allow the auditor direct access to all relevant documents 
and to schedule his/her time and the time of his/her staff to permit meetings with the auditor to 
discuss findings and any relevant issues. 
In addition, regulatory agencies may conduct a regulatory inspection of this study.  If such an 
inspection occurs, the Investigator agrees to allow the inspector direct access to all relevant 
documents and to schedule his/her time and the time of his/her staff to permit meetings with the 
inspector to discuss findings and any relevant issues. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 65 of 77 
 
10.0 
ETHICAL AND LEGAL ASPECTS 
The Principal Investigator and the study staff are responsible for conducting this study in 
accordance with the applicable principles which have their origins in the Declaration of Helsinki, 
ICH, GCPs, and all other applicable laws and regulations. 
This trial will be performed in compliance with the protocol and in accordance with Good Clinical 
Practice (International Conference on Harmonisation [ICH], Guidance E6), principles of human 
subject protection, and applicable country-specific regulatory requirements. 
10.1 
Institutional Review Board/Ethics Committee (IRB/EC) Approval 
This protocol, the Informed Consent, relevant supporting information and all types of subject 
recruitment or advertisement information must be approved by the appropriate IRB/EC before the 
study is initiated.  Any amendments to the protocol must also be approved, where necessary, by 
the IRB/EC prior to implementing changes in the study.  Documentation of these approvals must 
be provided to the Sponsor prior to the initiation of the amendment. 
The Investigator’s responsibilities regarding the IRB/EC are as follows:  
• Obtaining IRB/EC approval of the protocol, Informed Consent, and any advertisements to 
recruit subjects prior to their use. 
• Obtaining IRB/EC approval for any protocol amendments and Informed Consent revisions 
before implementing the changes. 
• Providing the IRB/EC with any required information before or during the study. 
• Submitting progress reports to the IRB/EC, as required, during the conduct of the study; 
requesting re-review and approval of the study, as needed; providing copies of all IRB/EC 
re-approvals and relevant communication to the Sponsor. 
• Notifying the IRB/EC within 10 days (unless required sooner by IRB/EC) of all serious 
and unexpected AEs related to the study medications that are reported to you by the 
Sponsor.  The Investigator is responsible for keeping the IRB/EC apprised of the progress 
of the study and of any changes made to the protocol as deemed appropriate, but in any 
case, at least once a year.  The Investigator must also keep the IRB/EC informed of any 
AEs, according to the IRB/EC policy. 
• Notifying Salix within 24 hours of awareness and the IRB/EC within in 10 days (unless 
required sooner by IRB/EC) of all unanticipated problems involving risk to subjects or 
others.  For the purposes of this study, an unanticipated problem is defined as any incident, 
experience, or outcome that meets all the following criteria:  

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 66 of 77 
 
o Unexpected in nature, severity, or frequency (i.e., not described in study-related 
documents such as the IRB-approved protocol or consent form, the Investigators 
brochure, etc.). 
o Related or possibly related to participation in the research (i.e., possibly related 
means there is a reasonable possibility that the incident experience, or outcome may 
have been caused by the procedures involved in the research). 
o Suggests that the research places subjects or others at greater risk of harm 
(including physical, psychological, economic, or social harm). 
10.2 
Subject Information and Informed Consent 
Informed consent will be obtained from each subject prior to conducting/obtaining any study-
related assessments including the discontinuation of any study prohibited medications.  An 
informed consent document that includes both information about the study and the consent form 
will be prepared and given to the subject.  The document must be in a language understandable to 
the subject and must specify who informed the subject.   
The Investigator’s draft Informed Consent Form (ICF) must be reviewed by Salix or its designee, 
prior to IRB/EC submission for approval.  An IRB/EC-approved copy of the ICF will be forwarded 
to Salix or its designee.  If during the study, the subject’s protected health information (PHI) is to 
be used or disclosed in a manner that is inconsistent with the informed consent that was provided, 
the Investigator must obtain a new authorization from the subject or a waiver of authorization from 
the IRB/EC or privacy board, as applicable.  If the ICF is amended during the study, the 
Investigator must follow all applicable regulatory requirements pertaining to approval of the 
amended Informed Consent Form by the IRB/EC and use of the amended form (including for 
ongoing subjects). 
The ICF documents the study-specific information the Investigator provides to the subject and the 
subject’s agreement to participate.  The Investigator will fully explain in layman’s terms the nature 
of the study, along with the aims, methods, anticipated benefits, potential risks, and any discomfort 
participation may entail.  The ICF must be appropriately signed and dated before the subject 
undergoes any study-related procedure.  The decision regarding subject participation in the study 
that is made either by the subject or the subject’s legally acceptable representative is entirely 
voluntary.  The Investigator or his/her designee must emphasize to the subject that consent 
regarding study participation may be withdrawn at any time without penalty or loss of benefits to 
which the subject is otherwise entitled. 
The ICF shall also contain the subject's authorization for the use and disclosure of his/her PHI in 
connection with the study.  The authorization shall include at a minimum a clear description of: 
the duration of the authorization, the subject's right of access to the PHI (or any suspension thereof 
during the course of the study), type of information to be used/disclosed in the study, the names or 
classes of parties that may use or disclose the PHI, the purpose of the use/disclosure of PHI, the 
extent of the subject's right to revoke the authorization, the extent to which participation in the 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 67 of 77 
 
study is conditioned on signing the authorization, and the potential for re-disclosure of PHI.  For 
purposes of this study, only those subjects participating in the study or the subject’s legally 
acceptable representative(s) will be allowed to sign the ICF.  This applies to all amended Informed 
Consent Forms as well.  
A separate healthy volunteer Inform Consent will be provided for flow cytometry assessment 
(approximately 25 subjects). These healthy volunteers will not be asked to take part in the study.  
The original and any amended signed and dated ICFs must be retained in the subject’s file at the 
study site; and a copy must be given to the subject or subject’s legally acceptable representative(s). 
10.3 
Study and Site Closure or Discontinuation 
Upon completion of the study, the following activities, when applicable, must be conducted by the 
monitor in conjunction with the Investigator, as appropriate: 
• Return of all study related data to Salix (or designee) 
• Accounting, reconciliation, and final disposition of used and unused study drug and 
placebo 
• Review of site study records for completeness 
In addition, Salix reserves the right to temporarily suspend or prematurely discontinue this study 
either at a single site or at all sites at any time and for any reason.  If such action is taken, Salix 
will discuss this with the Investigator (including the reasons for taking such action) at that time.  
Salix will promptly inform all other Investigators and/or institutions conducting the study if the 
study is suspended or terminated for safety reasons and will also inform the regulatory authorities 
of the suspension or termination of the study and the reason(s) for the action.  If required by 
applicable regulations, the Investigator must inform the IRB/EC promptly and provide the reason 
for the suspension or termination. 
10.3.1 
Study Discontinuation  
Should the Investigator, Salix, the FDA or local regulatory authorities become aware of conditions 
arising during the conduct of this study that may warrant the cessation of the study, such action 
may be taken.  Prior to such action, consultation between Salix, the Investigator, and, as 
appropriate, the FDA and/or local regulatory authorities will take place.  Conditions that may result 
in the termination of the study or parts thereof include, but are not limited to, the following: 
• The discovery of an unexpected, serious, or unacceptable risk to the subjects enrolled in 
the study. 
• A decision on the part of Salix to alter, suspend, or discontinue the development of the 
investigational product. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 68 of 77 
 
10.3.2 
Study Site Discontinuation 
The study site can be discontinued at the request of Salix, the Investigator, IRB/EC, or by the FDA 
or local regulatory authorities.  Conditions that may warrant discontinuation of the study site 
include, but are not limited to, the following: 
• The failure of the Investigator to accrue subjects into the study at an acceptable rate. 
• The failure of the Investigator to comply with applicable current regulations and/or GCPs. 
• The submission of knowingly false information from the research facility to the FDA, or 
other regulatory authorities. 
• Insufficient adherence to protocol requirements and procedures. 
If the study is prematurely discontinued, all study data must be returned to Salix or designee.  In 
addition, the site must conduct final disposition of all used and unused study drugs in accordance 
with Salix procedures for the study.  Study termination and follow-up will be performed in 
compliance with the conditions set forth in GCPs and applicable regulations.  Financial 
compensation to Investigators and/or institutions will be in accordance with the agreement 
established between the Investigator and Salix. 
10.4 
Handling and Record Keeping 
10.4.1 
Case Report Forms and Database Processing 
Subject data will be collected in an electronic Case Report Form (eCRF) using Electronic Data 
Capture (EDC) system.  The EDC system will be 21 CFR Part 11 compliant and will have a 
documented audit trail for all changes made to the eCRF.   
The Investigator or designee must enter all required subject data using the specified data collection 
method defined by Salix.  The Investigator must sign and date a declaration on the eCRF attesting 
to his/her responsibility for the quality of all data entered and that the data represents a complete 
and accurate record of each subject's participation in the study. 
Electronic case report form data will be provided to the Investigator at the end of the study and 
will need to be retained by the Investigator. 
10.4.2 
Source Documents 
Source documents consist of, but are not limited to, in-patient hospital charts, clinic notes, out-
patient records, original test results, laboratory data, worksheets, drug accountability records, 
consent forms, etc.  Source documents must be available for review and inspection during on-site 
monitoring of the study by Salix, their designees, IRB/IEC, and/or regulatory authorities. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 69 of 77 
 
10.4.3 
Subject Tracking 
A drug accountability log(s), subject identification log (to be retained by the Investigator only), 
and subject screening/enrollment data will be used to track subject participation in the study. 
10.4.4 
Study Files 
The investigational center will maintain a specific study file.  This file is subject to inspection as 
described under Section 9.2 and Section 9.3 of this protocol. 
10.4.5 
Data Management 
Data management will be performed in accordance with the standard operating procedures of Salix 
or its designee. 
10.5 
Confidentiality 
Anonymity of subjects participating in this study will be maintained.  Only subject numbers will 
be on any study documents submitted to the Sponsor.  Every effort will be made to maintain the 
confidentiality of documents that identify the subject by name (e.g., signed informed consent 
document, laboratory reports, clinic charts), except to the extent necessary to allow auditing by the 
FDA, or other regulatory authorities.  Should the name and/or address of a subject participating in 
this trial be on a document submitted to the FDA, or other regulatory authorities (e.g., laboratory 
report), the name and/or address will be completely blocked out and replaced with the subject 
number. 
The Investigator and other study site personnel will keep confidential any information provided 
by Salix (including this protocol) related to this study and all data and records generated while 
conducting the study, and will not use the information, data, or records for any purpose other than 
conducting the study.  These restrictions do not apply to: (1) information which becomes publicly 
available through no fault of the Investigator or study site personnel; (2) information which it is 
necessary to disclose in confidence to an IRB/IEC solely for the evaluation of the study; (3) 
information which it is necessary to disclose in order to provide appropriate medical care to a study 
subject, or (4) study results which may be published as described in Section 10.8.  If a written 
contract for the conduct of the study which includes confidentiality provisions inconsistent with 
this statement is executed, that contract’s confidentiality provisions shall apply rather than this 
statement. 
10.6 
Record Retention 
Essential documents as described above should be retained for one of the following time periods: 
• At least 2 years after the last marketing application in an ICH region and until there are no 
pending or contemplated marketing applications in an ICH region. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 70 of 77 
 
OR 
• At least 2 years have elapsed since the formal discontinuation of clinical development of 
the investigational product. 
These documents should be retained for a longer period however if required by applicable 
regulatory requirements or by an agreement with the Sponsor.  It is the responsibility of Salix to 
inform the Investigator/institution as to when these documents no longer need to be retained. 
10.7 
Financing and Insurance 
10.7.1 
Finance 
This study is supported by Salix Pharmaceuticals, Inc. a division of Bausch Health US, LLC.  
10.7.2 
Insurance and Indemnification 
Documentation of product liability insurance is on file at Salix and is available upon request. 
10.8 
Publication Policy 
The institution and the Investigator shall have the right, consistent with academic standards, to 
publish or present the results of the study, provided such publication or presentation does not 
disclose confidential information or other proprietary trade secrets of Salix.  Salix will work with 
the protocol development team to identify a lead author for manuscript development.  The 
manuscript authors will be determined by the amount of effort and participation each Investigator 
contributes towards the study design, the conduct of the study and the analysis of the study data.  
Prior to any publication, presentation or other disclosure, institution will submit the manuscript of 
any proposed publication (including abstracts, or presentation to a journal, editor, meeting, 
seminar, or other third party) to Salix at least sixty (60) days before publication, and Salix shall 
have the right to review and comment upon the proposed publication.  Upon the Sponsor's request, 
publication will be delayed up to ninety (90) additional days to enable Salix to secure adequate 
intellectual property protection for Salix’s property that could be affected by said publication.  
Salix shall have the right to require the deletion of any trade secret, or proprietary or confidential 
information of the Sponsor.  Any publication or disclosure by the institution or the Investigator 
shall give appropriate credit to the Sponsor.  Where title is not retained by the publisher, title to 
and the right to determine the disposition of any copyrightable material, first produced or 
composed in the performance of the study, shall remain with the institution.  With respect to such 
materials, the institution hereby grants to Salix an irrevocable, royalty-free, nonexclusive right to 
reproduce, translate, and use any such copyrighted material for its own research and commercial 
purposes.  The Investigator acknowledges and agrees that the study data and results may be 
disclosed by Salix to other clinical Investigators, the FDA, and other regulatory authorities. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 71 of 77 
 
10.9 
Ownership 
All data and records provided by Salix Pharmaceuticals, Inc., or Bausch Health Companies Inc. 
and its affiliates, or generated during the study (other than a subject’s medical records) and all 
inventions discovered during the course of conducting the study are the property of Salix.  If a 
written agreement is executed by the parties for the conduct of the study, which includes ownership 
provisions inconsistent with this statement, the ownership provisions contained in the written 
agreement between the parties shall control. 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 72 of 77 
 
11.0 
REFERENCES 
Centers for Disease Control and Prevention (CDC). Incidence of Sickle Cell Trait – United States, 
2010, 
2014. 
MMWR. 
2014, 
63(49);1155-1158. 
 
Obtained 
24 
April 
2020 
at: 
https://www.cdc.gov/ncbddd/sicklecell/features/keyfinding-trait.html 
da Guarda CC, Yahouédéhou SCMA, Santiago RP, Neres JSdS, Fernandes CFdL, et al. Sickle cell 
disease: A distinction of two most frequent genotypes (HbSS and HbSC). PLOS ONE. 2020, 15(1) 
Darbari, DS, Sheehan, VA, Ballas, SK. The vaso‐occlusive pain crisis in sickle cell disease: 
Definition, pathophysiology, and management. Eur J Haematol.; 2020, 105:237–246.  
Dutta D, Methe B, Amar S, et al. Intestinal injury and gut permeability in sickle cell disease. J 
Transl Med 2019, 17:183  
Dutta D, Li K, Methe B, Lim SH. Rifaximin on intestinally-related pathologic changes in sickle 
cell disease. Am J Hematol. 2020 Apr;95(4):E83-E86 
Lard LR, Mul FP, de Haas M, Roos D, Duits AJ. Neutrophil activation in sickle cell disease. J 
Leukoc Biol. 1999 Sep;66(3):411-5 
Lim SH, Fast L, Morris A. Sickle cell vaso-occlusive crisis: it's a gut feeling. J Transl Med. 2016 
Dec 1;14(1):334 
Lim SH, Morris A, Li K, Fitch AC, Fast L, Goldberg L, Quesenberry M, Sprinz P, Methé B. 
Intestinal microbiome analysis revealed dysbiosis in sickle cell disease. Am J Hematol. 2018 
Aug;93(4):E91-E93 
Lim SH, Dutta D, Moore J. Rifaximin for sickle cell disease. Am J Hematol. 2019 
Dec;94(12):E325-E328 
Manwani D, Frenette PS. Vaso-occlusion in sickle cell disease: pathophysiology and novel 
targeted therapies. Blood. 2013 Dec 5;122(24):3892-8 
Steinberg, M.H. and Sebastiani, P. (2012), Genetic modifiers of sickle cell disease. Am. J. 
Hematol., 2012, 87: 795-803 
Xu D, Gao J, Gillilland M 3rd, Wu X, Song I, Kao JY, Owyang C. Rifaximin alters intestinal 
bacteria and prevents stress-induced gut inflammation and visceral hyperalgesia in rats. 
Gastroenterology. 2014 Feb;146(2):484-96 
Yale SH, Nagib N, Guthrie T. Approach to the vaso-occlusive crisis in adults with sickle cell 
disease. Am Fam Physician. 2000, Mar 1;61(5):1349-56, 1363-4. Erratum in: Am Fam Physician 
2001 Jul 15;64(2):220 
Zhang, D., Chen, G., Manwani, D. et al. Neutrophil ageing is regulated by the microbiome. Nature 
2015, 525:528–532  
Zhang D, Xu C, Manwani D, Frenette PS. Neutrophils, platelets, and inflammatory pathways at 
the nexus of sickle cell disease pathophysiology. Blood. 2016 Feb 18;127(7):801-9 
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 73 of 77 
 
APPENDIX 1: 
SCHEDULE OF ASSESSMENTS 
Study Period  
Screening 
Treatment 
 
 
 
Follow-up 
During 
Visit to 
Medical 
Facility 
for VOC 
Study Day 
-21 to -1 
1 
8 (±1 
day) 
15 (±1 
day) 
29 (±1 
day) 
EOT/ET 
 
 
30 
 
 
     31 
 
 
32 
43 (±3 
days) 
EOS 
Visit Number a 
1 
2 
3 
4 
5 
6 
7 
8 
9 
 
Informed consent 
X 
 
 
 
 
 
 
 
 
 
Demographics 
X 
 
 
 
 
 
 
 
 
 
Medical history b (VOC 
history) 
X 
 
 
 
 
 
 
 
 
 
Eligibility criteria 
X 
X 
 
 
 
 
 
 
 
 
Height and Weight 
X 
 
 
 
  X j 
 
 
 
  X j 
 
Vital signs c 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Physical examination d 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
ECG e 
X 
X 
 
 
X 
 
 
 
  X e 
 
Hematology and 
Chemistry 
X 
X 
X 
X 
X 
 
X 
 
 X j 
X 
Hemoglobin genotype f 
X 
 
 
 
 
 
 
 
 
 
Coagulation Panel 
X 
 
 
 
 
 
 
 
 
 
HIV1 and HIV2 
X 
 
 
 
 
 
 
 
 
 
HBsAg, HBcAb, 
HBsAb, and HCV 
X 
 
 
 
 
 
 
 
 
 
Urinalysis 
X 
X 
X 
X 
X 
 
 
 
 X j 
X 
Pregnancy testing g 
X 
X 
 
 
X 
 
 
 
X 
 
Randomization 
 
X 
 
 
 
 
 
 
 
 
CANs 
 
X 
X 
X 
X 
 
X 
 
X 
X 
Serum CD62L 
 
X 
X 
X 
X 
 
X 
 
X 
X 
Serum iFABP 
 
X 
X 
X 
X 
 
X 
 
        X 
X 
Serum -LPS 
 
X 
X 
X 
X 
 
X 
 
X 
X 
Urine 3-indoxyl sulfate 
 
X 
X 
X 
X 
 
X 
 
X 
X 
PK Samples  
See Appendix 2 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 74 of 77 
 
VOCs h 
 
X 
X 
X 
X 
 
 
 
X 
 
Dispense Study Drug 
 
X 
X 
X 
 
 
 
 
 
 
Collect Study Drug 
 
 
X j 
X j 
X 
 
 
 
 
 
Assessment of  
Compliance 
 
 
X 
X 
X 
 
 
 
 
 
Adverse Events 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Concomitant 
X 
X 
X 
X 
X 
     X 
      X 
X 
X 
X 
Opioid use i 
X 
X 
X 
X 
X 
 
 
 
X 
X 
Abbreviations: CAN = circulating aged neutrophils; ECG = electrocardiogram; EOS = end of study; EOT = end of treatment; ET = early termination; hsCRP = high-sensitivity C-
reactive protein;  iFABP = intestinal fatty acid binding protein; LPS = Lipopolysaccharide PK = pharmacokinetics, VOC = vaso-oclusive crisis 
 
a. 
In case of situations that prevent a participant from attending a post-baseline study visit, a home health visit may be scheduled, where possible. The home health visit may 
include an assessment of changes in health and medications, measurement of vital signs and body weight, and checking of study medication compliance. The home health 
visit may also include all sample collections outlined in the study protocol (PK, hematology and urinalysis samples, urine sample for urine 3-inoxyl sulfate, and blood samples 
for CANs (if applicable), CD62L, iFABP and LPS). All documented assessments and laboratory results will be reviewed by the investigator and documented in relevant 
eCRFs as appropriate. 
b. 
Medical history will be obtained from prior 3 months. Detailed history of VOCs occurring over the past 12 months will be obtained. This will include collection of treatments 
for VOCs including drug, dose, route of admin, duration of treatment, and inpatient/outpatient setting. 
c. 
Vital signs will be obtained after the subject has been in a supine position for a minimum of 5 minutes.  Vital signs include systolic and diastolic blood pressure, heart rate, 
body temperature, and oxygen saturation.   
d. 
Perform a full physical examination at Screening and symptom-directed physical examination at subsequent visits. 
e. 
A 12-lead ECG  (supine) will be performed.  An ECG will be performed at the Day 43 (EOS) Visit only if abnormal findings were observed at the Day 29 (EOT/ET) Visit. 
f. 
Hemoglobin genotyping will be recorded if known.  If unknown at Screening, hemoglobin genotyping will be performed using HPLC/electrophoresis. 
g. 
Serum pregnancy test is to be performed at Screening for all women of childbearing potential. A negative Screening serum pregnancy test and a negative urine pregnancy test 
must be confirmed before randomization.  Subsequent pregnancy testing will be with urine pregnancy test.   
h. 
Information on whether a VOC requiring a visit to a medical facility occurred will be recorded.   Medications received during the VOC visit will be recorded. 
i. 
Only weight will be collected. 
j. 
Hematology, chemistry, and/or urinalysis will only be collected at this visit if needed for follow-up or resolution of AEs/SAEs. 
k. 
Not all treatment groups will return study drug at Visit 3 and Visit 4. 
l. 
During Screening, record all opioid use for the prior 30 days.  At each visit, record all opioid use since the previous visit. 
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 75 of 77 
 
 
APPENDIX 2: 
SCHEDULE FOR ACQUISITION OF PK SAMPLES  
 
 
Time (hours) Post-dose 
 
Pre-
Dose 
0.5 
1 
1.5 
2 
3 
4 
5 
8 
 
24 
 
30 
 
48 
 
72 
Day 1 
(Visit 2) 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
 
 
Day 8 
(Visit 3) 
X 
X 
X 
 
X 
 
 
 
 
 
 
 
 
Day 15 
(Visit 4) 
X 
X 
X 
 
X 
 
 
 
 
 
 
 
 
Day 29a 
(Visit 5) 
X 
X 
X 
X 
X 
X 
X 
X 
X 
  
X 
 
 
X 
 
X 
 
X 
During 
Visit for 
VOC 
PK sample obtained during visit, when possible, and estimated time from last dose 
recorded 
Abbreviations: VOC = vaso-occlusive crisis 
a.     Following the final dose on Day 29, blood samples will be collected pre-dose and at 0.5, 1, 1.5, 2, 3, 4,    
        5, 8,  24 (Visit 6), 30 (Visit 6), 48 (Visit 7), and 72 (Visit 8) hours post-dose. 
 
The windows around the collection timepoints are:  
• 
within 15 minutes prior to dose for pre-dose samples,  
• 
± 5 minutes for samples taken at 0.5 hours through 1.5 hours, and  
• 
±10 minutes for samples taken 2 hours through 8 hours. 
• 
±2 hours for samples taken 24 hours through 72 hours. 
 
 
 
 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 76 of 77 
 
APPENDIX 3: 
PROHIBITED CYP3A4, P-GP AND OATP1B1/B3 
INHIBITORS/INDUCERS  
 
The following table (not exhaustive) provides a list of prohibited drugs, herbal products, and 
foods.  Any questions or concerns should be referred to the Sponsor or designee.  
 
CYP3A4 Inhibitors 
Drugs  
amprenavir, aprepitant, atazanavir, boceprevir, 
ciprofloxacin, clarithromycin, cobicistat, conivaptan, 
crizotinib, cyclosporine, danoprevir, darunavir, 
diltiazem, dronedarone, elvitegravir, erythromycin, 
faldaprevir, fluconazole, idelalisib, imatinib, indinavir, 
isavuconazole, itraconazole, ketoconazole, mibefradil, 
nefazodone, nelfinavir, netupitant, nilotinib, 
posaconazole, ribociclib, ritonavir, saquinavir, telaprevir, 
telithromycin, tofisopam, troleandomycin, verapamil, 
voriconazole  
Herbals and 
Foods  
grapefruit juice, Schisandra sphenanthera extract  
CYP3A4 Inducers 
Drugs  
bosentan, carbamazepine, dabrafenib, efavirenz, 
enzalutamide, etravirine, genistein, lopinavir, 
lumacaftor, mitotane, modafinil, nafcillin, phenobarbital, 
phenytoin, rifabutin, rifampicin[rifampin], telotristat, 
thoridazine  
Herbals and 
Foods  
St. John's wort  
P-gp Inhibitors 
Drugs  
alogliptin, amiodarone, azithromycin, canaglifozin, 
captopril, carvedilol, clarithromycin, clopidrogel, 
cobicistat, conivaptan, cremophor EL and RH40, 
daclatasvir, diltiazem, dronedarone, eliglustat, 
erythromycin, felodipine, fluvoxamine, fostamatinib, 
glecaprevir, isavuconazole, itraconazole, ivacaftor, 
ketoconazole, lapatinib, lasmiditan, ledipasvir, lopinavir, 
mibefradil, mirabegron, nifedipine, nitrendipine, 
paroxetine, pibrentasvir, propafenone, quinidine, 
quinine, ranolazine, rifampicin[rifampin], ritonavir, 
rolapitant, saquinavir, sarecycline, simeprevir, 
suvorexant, talinolol, telaprevir, telithromycin, 
telmisartan, ticagrelor, tipranavir, tolvaptan, valspodar, 
vandetanib, velpatasvir, vemurafenib, verapamil, 
voclosporin, vorapaxar, voxilaprevir  
Herbals and 
Foods  
Ginkgo biloba, milk thistle, quercetin, Schisandra 
chinensis extract, St. John's wort, curcumin  
P-gp  
Inducers 
Drugs  
carbamazepine, 
efavirenz, 
indinavir, 
nelfinavir,
phenytoin, rifampicin[rifampin]  
Herbals and 
Foods  
danshen, genistein  
OATP1B1/OATP1B3 Inhibitors 
atazanavir, clarithromycin, cyclosporine, erythromycin, 
gemfibrozil, lopinavir and ritonavir, rifampin (single 
dose), simeprevir 

Protocol RBSC2161; Version 6.0, 12 April 2022 
 
Salix Pharmaceuticals, Inc 
 
CONFIDENTIAL 
 Page 77 of 77 
 
Cobicistat, Daclatasvir, Eltrombopag, Glecaprevir, 
Letermovir, Paritaprevir, Pibrentasvir, Sacubitril, 
Saquinavir, Telithromycin, Teriflunomide, Tipranavir, 
Velpatasvir, Voclosporin, Voxilaprevir 
horny goat weed and milk thistle 
 
Prohibited substances compiled from multiple sources, including:  
1. FDA DDI Index Inhibitors and Inducers (https://www.fda.gov/drugs/drug-interactions-labeling/drug-
development-and-drug-interactions-table-substrates-inhibitors-and-inducers)  
2. Flockhart Table at Indiana University (https://drug-interactions.medicine.iu.edu/Home.aspx) 
3. UW DIDB (https://www.druginteractionsolutions.org/solutions/drug-interaction-database/) Prescriber’s 
Information for FDA approved products 
Ali et al., The involvement of human organic anion transporting polypeptides (OATPs) in drug-herb/food 
interactions, Chin Med. 2020 Jul 9;15:71. doi: 10.1186/s13020-020-00351-9. eCollection 2020.