A Study of ABI-2280 Vaginal Insert (Previously Referred to as ABI-2280 Vaginal Tablet) in Participants With Cervical Intraepithelial Neoplasia

Inclusion Criteria: * Women, 25 to 55 years old. * For Cohorts A1 and A2 in Part A, participants with biopsy-confirmed CIN (with visible lesions) regardless of p16 positivity may be enrolled upon consultation with PI and Medical Monitor. These participants will not be required to get LLETZ if not medically necessary, as determined by the PI in consultation with the Medical Monitor. * For Cohorts A3 and above in Part A and Part B POC cohorts, biopsy-confirmed cHSIL that is p16+ (p16INK4a expressed) within 60 days of enrollment (dosing) with no evidence of invasive cancer in any specimen. If biopsy was performed ≥ 60 days before planned enrollment, participants must agree to have another biopsy performed at the Screening visit, unless approved by the Medical Monitor. * A positive high-risk HPV (hrHPV) result by provider-obtained cervical swab at screening or previously obtained and documented within the past 3 months. * No prior treatment for Cervical intraepithelial neoplasia (CIN). * Generally, in good health with no clinically significant pulmonary, cardiac, gastro-enterologic, neurologic, renal, musculoskeletal, rheumatologic, metabolic, neoplastic, or endocrine disease. Exclusion Criteria: * Women who are pregnant, plan to become pregnant in the next 4 months, or lactating females. * Unwilling to use stringent methods of contraception (including barrier method, as well as another acceptable method) throughout the course of the study. * History of cancer, except basal cell or squamous cell carcinoma of the skin. * History of genital herpes with outbreak within prior 12 months. * Have an active pelvic or non-HPV (Human papillomavirus) vaginal infection (e.g., that was detected by a positive urine screen for gonorrhea or chlamydial infection, bimanual exam consistent with pelvic inflammatory disease, positive bedside testing criteria for bacterial vaginosis, candida vaginitis or trichomonal vaginitis, etc). * Current or recent abnormal vaginal discharge and /or abnormal vaginal bleeding. * Had a therapeutic abortion or miscarriage less than 3 months prior. * Any clinically significant immune suppressing condition. * Participants with a significant acute condition or any other condition that in the opinion of the Investigator might interfere with the evaluation of the study objectives. * Women who, in the PI's judgment, would be harmed by the delay in undergoing definitive treatment as a result of study participation and the ABI-2280 Vaginal Tablet dosing schedule. * Vaccination (even 1 dose) with a prophylactic HPV vaccine (i.e., Gardasil®, Gardasil®-9 or Cervarix®) in the last 3 months. * Vaccination with a therapeutic HPV vaccine. * Other inclusion/exclusion criteria may apply