A Study to Evaluate the Safety, Tolerability and Efficacy of MHV370 in Participants With Sjogren's Syndrome (SjS) or Mixed Connective Tissue Disease (MCTD)

Inclusion Criteria:

SjS and MCTD:

• Fully vaccinated with any locally approved COVID-19 vaccination including booster vaccinations if required by local guidelines

SjS:

• Unstimulated whole salivary flow rate of > 0 mL/min at screening

• Classification of Sjögren's Syndrome according to the 2016 ACR/EULAR criteria atscreening

• Screening ESSDAI (based on weighted score) ≥ 5 from 8 defined domains (biologic,hematologic, articular, cutaneous, glandular, lymphadenopathy, renal,constitutional).

MCTD:

• Diagnosis of MCTD based on criteria like a) Raynaud's phenomenon b) At least two ofthe four following signs: i) synovitis, ii) myositis, iii) swollen fingers and vi)interstitial lung disease

• Patients with overlap syndromes, i.e. patients meeting diagnostic criteria forsystemic autoimmune disease other than MCTD may be included unless they have majororgan involvement as judged by the investigator

Exclusion Criteria:

SjS and MCTD:

• Prior use of B-cell depleting therapy within 6 months of baseline. For participantswho received B-cell depleting therapy within 6 -12 months of baseline visit, B-cellcount should be within normal range

• Prior treatment with any of the following within 3 months of baseline: CTLA4-Fc Ig (abatacept), Anti-TNF mAb, Intravenous Ig, Plasmapheresis, i.v. or oralcyclophosphamide, i.v. or oral cyclosporine A

• Screening CBC laboratory values as follows: Hemoglobin levels < 8 g/dL (< 5 mmol/L),Total leukocyte count < 2,000/µL (2 x 109/L), Platelets < 50,000/µL (50 x 109/L),Neutrophil count < 1,000/µL (1 x 109/L)

• Pregnant or nursing (lactating) women

• Women of child-bearing potential, defined as all women physiologically capable ofbecoming pregnant, unless they use a highly effective method of contraception

SjS:

• Sjögren's Syndrome overlap syndromes where another autoimmune disease constitutesthe primary illness

• Required regular use of medications known to cause, as a major side effect, drymouth / eyes

Other protocol-defined inclusion/exclusion criteria may apply