A Phase 2 Study to Evaluate the Safety and Immunogenicity of Two Oral Poliovirus Vaccine Candidates

This study is designed to evaluate the safety and immunogenicity of two novel type 2 oral poliovirus vaccine (nOPV2) candidates (nOPV2 candidate 1 and nOPV2 candidate 2) in adults. The primary objectives of the study include the general safety and immunogenicity of the two candidate vaccines in healthy volunteers previously vaccinated with Sabin monovalent OPV or inactivated polio vaccine (IPV) only.

Two nOPV2 vaccine candidates have been developed as attenuated serotype 2 polioviruses derived from a modified Sabin 2 infectious complementary deoxyribonucleic acid (cDNA) clone. nOPV2 Candidate 1 (S2/cre5/S15domV/rec1/hifi3) and nOPV2 Candidate 2 (S2/S15domV/CpG40) were generated by modifying the Sabin-2 ribonucleic acid (RNA) sequence to improve phenotypic stability and make the strains less prone to reversion to virulence. The novel vaccine will eventually be licensed based on 3 criteria: a similar safety profile to the currently licensed monovalent OPV2 (mOPV2) of the Sabin strain, non-inferior immunogenicity, and reduced reversion to virulence.

Due to the withdrawal of Sabin monovalent oral polio vaccine type 2 and prohibition of its use from April 2016 onward, well before the availability of nOPV2 for clinical testing, a head to head comparison of nOPV2 and mOPV2 is not possible. For these reasons, Phase 4 trials have been conducted with Sabin mOPV2 to provide control data on safety, immunogenicity, against which data for nOPV2 in subsequent Phase I and II studies will be evaluated and compared. The Phase 4 trials of Sabin mOPV2 were designed to parallel the expected design of the Phase 1 and 2 nOPV2 studies with respect to overall design, inclusion of similar study cohorts.

This study is designed to evaluate the safety and immunogenicity of two novel type 2 OPV candidates in adults before testing in young children and then infants. The study will include both OPV-vaccinated and IPV-vaccinated adults to provide safety and immunogenicity data relevant to the decision to advance to future studies with testing in children who have not been exposed to OPV2. The primary objectives of the study include the general safety and immunogenicity of the two candidate vaccines, primarily based on comparison with historical data obtained in a Phase 4 study of Sabin mOPV2 for OPV-vaccinated subjects, in order to establish non-inferior immunogenicity and acceptable safety profile. Assessment of the general safety of the 2 candidate vaccines in IPV-only vaccinated participants will be based on comparison with data from a placebo group.

The phase 4 control study (UAM1) used for the comparison in this study is registered with EudraCT (2015-003325-33). Participants were healthy adults aged 18-50 years with documented history of at least three polio vaccinations, including OPV, and were randomly assigned to either one dose or two doses of monovalent OPV2. Between January and March 2016, 100 volunteers were enrolled and randomly assigned to receive one or two doses of monovalent OPV2 (n=50 in each group).

Eligibility Criteria:
Inclusion Criteria:

1. For Groups 1, 2, 3 and 4: healthy males or females, from 18 to 50 years of age inclusive, having previously received at least 3 doses of OPV more than 12 months before the start of the study;
2. For Groups 5, 6 and 7: healthy males or females, from 18 to 50 years of age inclusive, having previously received at least 3 doses of IPV more than 12 months before the start of the study;
3. Having residence in Belgium;
4. In good physical and mental health as determined on the basis of medical history and general physical examination performed at Day 0;
5. Female subjects of childbearing potential must agree to the use of an effective method of birth control throughout the study and up to 3 months after last vaccine dose;
6. Willing to adhere to the prohibitions and restrictions specified in this protocol;
7. Informed Consent Form (ICF) and Code of Conduct signed voluntarily by the subject before any study-related procedure is performed, indicating that the subject understands the purpose of any procedures required for the study and is willing to participate in the study.

Exclusion Criteria:

1. A condition that, in the opinion of the Investigator, could compromise the well-being of the subject or course of the study, or prevent the subject from meeting or performing any study requirements;
2. For Groups 5, 6 and 7: ever having received any OPV in the past;
3. Any travel to polio endemic countries or countries with evidence of recent (within last 6 months) wild or vaccine-derived poliovirus circulation during the total duration of the study;
4. Professional handling of food, catering or food production activities during the total duration of the study;
5. Having Crohn's disease or ulcerative colitis or having had major surgery of the gastrointestinal tract involving significant loss or resection of the bowel;
6. A known allergy, hypersensitivity, or intolerance to the study vaccine or the placebo, or to any of their components or to any antibiotics;
7. Any confirmed or suspected immunosuppressive or immunodeficiency condition (including human immunodeficiency virus \[HIV\] infection, hepatitis B or C infections or total serum immunoglobulin A \[IgA\] level below laboratory lower limit of normal \[LLN\]);
8. Will have household or professional contact with known immunosuppressed people or people without full polio vaccination (i.e. complete primary infant immunization series), e.g. babysitting during the total duration of the study;
9. Neonatal nurses or others having professional contact with children under 6 months of age during the total duration of the study;
10. Chronic administration (i.e., longer than 14 days) of immunosuppressant drugs or other immune-modifying drugs within 6 months prior to the first vaccine dose or planned use during the study. For instance, for corticosteroids, this means prednisone, or equivalent, ≥ 0.5 mg/kg/day (inhaled and topical steroids are allowed whereas intra-articular and epidural injection/administration of steroids are not allowed);
11. Presence of contraindications to administration of the study vaccine on Day 0: acute severe febrile illness deemed by the Investigator to be a contraindication for vaccination or persistent diarrhea or vomiting;
12. Indications of drug abuse or excessive use of alcohol at Day 0 (males: \> 21 units/week; females \> 14 units/week);
13. Being pregnant or breastfeeding. Women of childbearing potential will undergo a urine pregnancy test at each vaccination visit. Subjects with a positive pregnancy test will be excluded;
14. Participation in another clinical study within 28 days prior to entry in this study or receipt of any investigational product (drug or vaccine) other than the study vaccine within 28 days prior to the first administration of study vaccine, or planned use during the study period;
15. Administration of any vaccine other than the study vaccine within 28 days prior to the first dose of study vaccine and during the entire study period;
16. Administration of any polio vaccine within 12 months before the start of the study;
17. Having had a transfusion of any blood product or application of immunoglobulins within the 4 weeks prior to the first administration of study vaccine or during the study;
18. Subject is an employee of the Investigator or study site, with direct involvement in the proposed study or other studies under the direction of that Investigator or study site, or is a family member of an employee or the Investigator, or was a study subject in the historical control studies UAM1 or UAT1 or in the study UAM4a (NCT03430349);
19. Having a family or household member participating in the study CVIA 065 (NCT04232943) or being a study subject in the study CVIA 065.