A study to investigate the efficacy and safety of subcutaneous sonelokimab versus placebo in participants aged 18 years and over with active psoriatic arthritis who are naive to biologic DMARDs

Prior treatment

• Participants who have had major surgery (including joint surgery) within 6 months before the Baseline Visit or are planning to have major surgery during the study.
• Participants who have received a live (including attenuated) vaccination within 8 weeks before the Baseline Visit or plan to receive a live vaccination during the study and up to 8 weeks after the last dose of study treatment. Examples of restricted vaccinations include, but are not limited to: (a) Zoster vaccine live (Zostavax). (b) Measles-mumps-rubella or measles-mumps-rubella-varicella. (c) Monovalent live attenuated influenza A (intranasal). (d) Oral polio. (e) Rotavirus. (f) Seasonal trivalent live attenuated influenza (intranasal). (g) Smallpox. (h) Oral typhoid. (i) Varicella (chicken pox). (j) Yellow fever.
• Participants who have an active infection or history of infections, including any of the following: a. Any infection (exception: common cold) requiring systemic treatment within 14 days before the Baseline Visit. b. Serious infection, defined as infection requiring hospitalization or intravenous anti-infective treatment, within 2 months before the Baseline Visit. c. History of opportunistic infections caused by uncommon pathogens (eg, Pneumocystis jirovecii, Blastomyces, aspergillus, cryptococcosis), or severe infections caused by common pathogens (eg, cytomegalovirus, severe herpes zoster [ie, multidermatomal herpes zoster, herpes zoster with organ involvement, ophthalmic herpes, or recurrent herpes zoster, defined as 2 episodes within 2 years before the Baseline Visit]). d. History of other opportunistic, recurrent, or chronic infections that, in the opinion of the investigator, might cause study participation to be detrimental to the participant. e. Candida infection requiring systemic therapy for ≥7 days in the last 12 months before the Baseline Visit. f. Any history of esophageal or systemic candidiasis. g. Current active candidiasis or Candida infection within the 1 month before the Baseline Visit. h. Concurrent acute or chronic viral hepatitis B or C, or human immunodeficiency virus (HIV).
• Participants who have experienced a period of ≥3 consecutive weeks of unexplained diarrhea in the 24 weeks before the Baseline Visit.
• Previous exposure to sonelokimab.
• Participants who have ever received: (a) Any biologic immunomodulating agents for PsA or PsO, whether investigational or approved. (b) Any investigational agent for PsA or PsO, if given ≤ 5 half-lives prior to randomization. (c) Any biologic treatment for any other indication, if given ≤ 5 half-lives prior to randomization.
• Participants with erythrodermic, guttate, or pustular form of PsO or drug-induced PsO.
• Participants with primary immunodeficiencies, prior splenectomy, or suppressive conditions, including participants taking immunosuppressive therapy following organ transplants.

Other illness

• Participants with a known hypersensitivity to sonelokimab or any of its excipients.
• Participants who have a diagnosis of chronic inflammatory conditions other than PsO or PsA, including but not limited to rheumatoid arthritis, reactive arthritis, enteropathic arthritis, ankylosing spondylitis, sarcoidosis, atopic dermatitis, and systemic or cutaneous lupus erythematosus.
• Participants with severe cardiovascular comorbidities including but not limited to: documented history of myocardial infarction, unstable angina pectoris stroke, presence of heart failure (New York Heart Association classification III or IV), or evidence of severe, uncontrolled hypertension (characterized by 2 BP measurements separated by ≥15 minutes with systolic BP >180 mmHg or diastolic BP >120 mmHg).
• Participants with any other clinically significant medical conditions or any other reason, including any medical or surgical procedure or any physical, psychological, or psychiatric condition that could, in the opinion of the investigator, compromise the participant’s safety, interfere with their participation in the study, make the participant an unsuitable candidate to receive study treatment, or put the participant or study data at risk.
• Participants with clinically significant ECG abnormalities on centrally read ECG at the Screening Visit. Clinically significant ECG abnormalities are considered changes that often indicate underlying cardiac conditions that may require immediate medical attention.
• Participants who have a history of chronic alcohol or drug abuse in the past year before the Screening Visit.
• Participants with a confirmed or suspected diagnosis of inflammatory bowel disease (eg, ulcerative colitis or Crohn’s disease), either in medical history or currently present.
• Participants with evidence of TB infection (active, history of active, latent or history of latent) at the Screening Visit.
• Participants with any current nontuberculous mycobacterial infection or any history of nontuberculous mycobacterial infection at the Screening Visit.
• Participants with any condition that in the investigator’s judgement may potentially interfere with study efficacy assessments, including but not limited to fibromyalgia and reactivated osteoarthritis.
• Participants with a history of a lymphoproliferative disorder, including lymphoma, or current signs and symptoms suggestive of lymphoproliferative disease.

Lab values

• Participants with laboratory abnormalities at the Screening Visit, including any of the following: (a) Aspartate aminotransferase (AST), alanine aminotransferase (ALT), or alkaline phosphatase (ALP) >3×upper limit of normal (ULN). (b) Serum direct bilirubin >1.5×ULN. (c) White blood cell count <3.0×10^9/L. (d) Absolute neutrophil count <1.5×10^9/L. (e) Absolute lymphocyte count <0.8×10^9/L. (f) Platelet count <100×10^9/L. (g) Hemoglobin <85 g/L. (h) Creatinine clearance <30 mL/min
• Any other laboratory abnormality that could, in the opinion of the investigator, compromise the participant’s safety, prevent the participant from completing the study, or interfere with the interpretation of the study results.

Age

• Participants with a concurrent malignancy or a history of malignancy during the past 5 years of the Baseline Visit, with the following exceptions: a. ≤3 excised or ablated basal cell carcinomas of the skin. b. One squamous cell carcinoma of the skin not worse than Stage T1 that has been successfully excised or ablated (no other previous treatments allowed), with no signs of recurrence or metastases for ≥2 years before the Baseline Visit. c. Actinic keratosis. d. Squamous cell carcinoma in situ of the skin successfully excised or ablated at >6 months before the Baseline Visit. e. Localized carcinoma in situ of the cervix, treated and considered cured.

Other

• Participants who currently use or plan to use one or more of the prohibited treatments specified in this protocol (unless permitted according to criteria in protocol Section 6.9)
• Participants who are an employee or a direct relative of an employee of the sponsor, a study center, or a third-party organization involved in the study.
• Participants who currently, or in their history, have an established diagnosis of arthritis mutilans. Note: participants with any other PsA clinical subtype (eg, symmetrical polyarthritis, asymmetrical oligoarthritis, distal interphalangeal arthritis, and arthritis with axial involvement) are eligible for the study.

• Participants must be ≥18 years of age at the time of signing the informed consent.
• Male participants must be willing to use a condom when sexually active with a partner of childbearing potential during the study and for at least 8 weeks after the last dose of study treatment, unless surgically sterile. Male participants must also agree to refrain from donating sperm during the study and for at least 8 weeks after the last dose of study treatment.
• Participants are considered reliable and capable of adhering to the protocol, visit schedule, or medication intake, according to the judgment of the investigator.
• Participants are able to understand and provide signed informed consent (see protocol Appendix 1).
• Participants who have a confirmed diagnosis of PsA per the 2006 Classification for Psoriatic Arthritis (CASPAR) criteria with symptoms for ≥6 months before the Screening Visit.
• Participants who have active disease (defined by a 68 tender joint count [TJC68] of ≥3 and a 66 swollen joint count [SJC66] of ≥3 at Screening Visit and confirmed at Randomization Visit).
• Participants who have current active plaque PsO with ≥1 psoriatic plaque of ≥2 cm or nail changes consistent with PsO or a dermatologist-confirmed personal history of plaque PsO.
• Participants who test negative for both rheumatoid factor and anti-cyclic citrullinated peptide at the Screening Visit.
• Participants should have (a) been taking a stable dose of NSAIDs for a period of ≥4 consecutive weeks, any time prior to screening, with inadequate control of symptoms, or (b) should have a documented intolerance or contraindication to ≥1 NSAID.
• Participants should have had an inadequate response to ≥1 nonbiological conventional synthetic DMARDs (csDMARDs) [methotrexate, sulfasalazine, leflunomide], taken for at least 12 weeks (with a stable dose for ≥8 weeks), or should have a documented intolerance to or contraindication to at least one of these csDMARDs as defined by the investigator. Note: in case csDMARDs were discontinued before enrollment in this study, the washout requirements in Section 6.9 (Table 7) should be followed.
• Participants must have the presence of at least one of the following at the Screening Visit: (a) ≥1 erosion based on the Screening plain X-rays of hands and feet, as determined by centralized imaging review. (b) A hs-CRP value greater than the central laboratory-defined upper limit of normal.
• Female participants are eligible to participate if they are not pregnant or breastfeeding and must be of nonchildbearing potential or (if women of childbearing potential [WOCBP]) must agree to use highly effective methods of contraception during the study and for at least 8 weeks after the last dose of study treatment. WOCBP must have a negative urine pregnancy test at screening and a negative urine pregnancy test at Week 0/Day 1 before initiation of study treatment. Female participants of childbearing potential must refrain from donating oocytes during the study and for at least 8 weeks after the last dose of study treatment. See Appendix 4 for the definitions of nonchildbearing potential, childbearing potential, and highly effective methods of contraception.