Inclusion Criteria:

Subjects are eligible for enrollment in the study only if they meet all of the following
criteria:

   - Have given written informed consent

   - Are men or women aged 18 to 85, inclusive, at the time of initial screening

   - Have a confirmed diagnosis of primary Sjogren's syndrome by the 2016 ACR-EULAR
   classification criteria for primary Sjogren's syndrome [2]

   - ≥50mm on a visual analog scale (VAS) for ocular dryness or oral dryness or ≥5 on the
   ESSPRI score for dryness

   - Have a Hočevar salivary gland ultrasound score (SGUS) (on a 0-48 point scale) and ≥10
   [to detect relatively early disease with less anatomic derangement that will
   potentially be more responsive to treatment and to exclude patients with no changes on
   ultrasound that would preclude an ability to see improvement] [3]

   - All women (regardless of childbearing potential) must test negative for pregnancy at
   the time of screening. Women must also agree to use a reliable method of birth control
   from screening until 12 weeks following last dose of study drug (adequate
   contraceptive measures include: intrauterine devices, hormonal contraceptives,
   complete sexual abstinence, or vasectomized partner), unless they are not of
   child-bearing potential as defined by meeting either of the following:

      - Are at least 6 weeks after bilateral oophorectomy, tubal ligation, or
      hysterectomy

      - Are postmenopausal, as defined by having had spontaneous amenorrhea for at least
      12 months and a follicle-stimulating hormone level >40 mIU/mL at screening

   - Have venous access sufficient to allow for blood sampling, as per the protocol

   - Are reliable and willing to make themselves available for the duration of the study
   and are willing to follow study procedures

Exclusion Criteria:

   - Prior treatment with a BTLA agonist within 6 months before baseline

   - Use of other biologic agents including TNF inhibitors, abatacept, IL-6 inhibitors, or
   BAFF inhibitors within 8 weeks prior to baseline

   - Use of a B cell depleting therapy (such as rituximab) within 12 months prior to
   baseline

   - A history of, or current, inflammatory or autoimmune disease (that could affect the
   interpretation of safety or efficacy outcomes) other than primary Sjogren's syndrome

   - Evidence of active tuberculosis, HIV, or hepatitis B or C infection

   - Have a diagnosis or history of malignant disease within 5 years prior to baseline,
   with the following exceptions: basal cell or squamous epithelial carcinomas of the
   skin that have been resected with no evidence of metastatic disease for 3 years and/or
   cervical carcinoma in situ, with no evidence of recurrence within the 5 years prior to
   baseline

   - Prior LASIK or radial keratotomy surgery which could affect symptomatic complaints of
   eye dryness