This study focuses on a genetic condition that affects the Janus Kinase-Signal Transducer and Activator of Transcription (JAK-STAT) immune signaling pathway. A specific change in the DNA leads to overactivation of this pathway, which can result in immune dysregulation and related clinical symptoms.

Currently, five genetic mutations are known to cause these JAK-STAT pathway driven immune disorders: STAT1, STAT3, STAT5B, STAT6, and JAK1 (collectively referred to as JAK-STAT disorders). This study is a basket clinical trial, meaning patients with these different but related genetic conditions are enrolled in the same study and treated with the same investigational therapy.

The purpose of this study is to evaluate the safety and tolerability (ability to tolerate) of a drug called Upadacitinib in patients with JAK-STAT disorders with activating mutations. This drug belongs to a class of drug called Janus kinase (JAK) inhibitors, also known as JAKinibs. It is a type of immune system modulating medication that regulates (fixes) the JAK- STAT signaling pathway. Upadacitinib has been approved by the FDA for multiple immunological diseases and disorders. Presently, there is no FDA approved treatment for this group of JAK-STAT disorders. The study will also investigate immune factors in the blood to develop diagnosis methods that can be used in the future for better medical management of these disorders.

The study consists of four phases: screening phase, open label phase, randomized withdrawal phase and maintenance phase. The study will last approximately 12 months. While in the study, participants will receive a once daily dose of Upadacitinib that best helps control their disease. During the study participants will be asked to answer questions about their health and medical history. They will also complete physical exams, blood tests, and other questionnaires.

This is a phase 1/2, multi-center trial with an open label dose-escalation phase (OL) followed by a double-blind placebo-controlled randomized withdrawal phase (RW) to study the safety, tolerability, and preliminary efficacy of Upadacitinib in patients with confirmed and symptomatic gain of function mutations in the JAK-STAT pathway. Upon completion of the randomized withdrawal phase, each patient will enter the maintenance phase (MP) where all patients will receive Upadacitinib.

OL Phase (16 weeks): The subject will be escalated two times if tolerated and clinically indicated based upon disease response. The starting dose will be 15 mg per day for patients greater than or equal to 12 years of age (and at least 30 kg in weight). The subject will remain at this dose level for 28 days. The subject will visit the clinical site on day 1 of each dose escalation visit and then will be remotely monitored (phone call and laboratory monitoring to check complete blood counts) on Day 3 and Day 10.

Patients must have a disease status score of 2 or higher utilizing the Primary Immune Regulatory Deficiency (PIRD) Disease Modules prior to initiation of dose-escalation of the drug. The PIRD score is a disease scoring method that capture the clinical manifestations of all PIRDs including JAK/STAT GOF disorders. The PIRD scores for clinical improvement across organ systems for each patient will standardize the ability to quantify improvement across divergent disease phenotypes and assess outcomes based on clinical improvement within each disorder. Patients who demonstrate a response to study treatment, as determined by improvement in PIRD score, may proceed to the RW Phase. Patients who do not meet eligibility criteria for the RW Phase will enter MP.

During the OL Phase, the optimal treatment dose (OTD) for each patient will be determined. OTD will be defined as the dose that achieved complete response or partial response based on the PIRD scores.

RW Phase (8 weeks): For the double-blind randomized withdrawal phase, patients will be randomized to receive either the Optimum tolerated dose (OTD) dose from the OL phase or Placebo using a 1:1 randomization ratio. Subject will come to the study site every 4 weeks. The subject can discontinue the RW phase if he/she experiences a flare (worsening of disease symptoms) and will enter the Maintenance Phase outlined below. For measuring disease flare Primary Immune Regulatory Disorders (PIRD) score will be used. It will be deemed a flare if the score increases by ≥1 in disease manifestation. During the RW-phase, the reference for a disease flare (for the primary endpoint assessment) will be the end of the OL phase PIRD score.

MP Phase (28 weeks): Subject will be monitored closely for any drug related toxicities (blood counts, lipid and metabolic panels) and continue to take the highest tolerated dose level attained during the escalation phase. The subject will return to the clinical site on day 168, day 217, day 266, day 315 and day 364. Upon conclusion of the maintenance phase at day 364 the study team will safely transition the subject to clinically viable treatment alternatives that are commercially available (after a 3 days washout period for Upadacitinib).

Inclusion Criteria:

• At least 30kg
• Patients with a confirmed JAK/STATGOF mutation with evidence of immune dysregulation
• Current disease status meeting criteria as defined in the disease scoring module
• Expected survival of more than 12 months
• Willingness to allow storage of biological samples for future research
• Agreement to use highly effective contraception (for female participants)

Exclusion Criteria:

• Hypersensitivity to the study drug or any medication in the same class
• Active infections
• Central nervous system (CNS) manifestations
• Pregnancy
• Medical conditions or use of concomitant medications that may interfere with the effect or evaluation of the study drug
• Laboratory abnormalities as specified in the protocol
• Receipt of a live vaccine within 30 days prior to study treatment
• High risk or history of osteoporosis, thrombosis, gastrointestinal (GI) perforation, or malignancy

Double Blinded