Open-label Single-Center Study to Evaluate the Safety and Efficacy of Combining Rituximab and AB-101 in B-cell Associated Autoimmune Diseases.

Inclusion Criteria:

General Inclusion Criteria (applicable to subjects in all 4 studied indications)

1. Males or female subjects, ≥ 18 years of age at the time of signing informed consent.

2. Ability to understand the requirements of the study.

3. Willingness to provide written informed consent.

4. Willingness to comply with the study protocol procedures.

5. Women of childbearing potential and all male participants must agree to use twoacceptable methods of contraception together to avoid pregnancy. The following areexamples of acceptable methods of contraception including:

6. Established use of oral, inserted, injected, or implanted hormonal methods ofcontraception.

7. Correctly placed copper containing intrauterine device (IUD).

8. Male condom or female condom used WITH a spermicide (i.e., foam, gel, film,cream, suppository).

9. Male sterilization with appropriately confirmed absence of sperm in thepost-vasectomy ejaculate.

10. Bilateral tubal ligation or bilateral salpingectomy.

11. Oral steroids will be tapered to <20 mg/day of prednisone (or equivalent) at least 1week prior to the first study treatment. The tapering schedule will be at thediscretion of the Investigator.

12. Subjects must have a predicted diffusing capacity for carbon monoxide (DLCO) of >60%and a forced expiratory volume 1 (FEV1) >70% at screening.

13. Left ventricular ejection fraction (LVEF) ≥ 45% by Echocardiogram. Rituximab andAB-101 in autoimmune diseases Clinical Study Protocol V. 1.1 Confidential Page 11 of 101 April 16, 2024

14. Baseline laboratory values fulfilling the following requirements to demonstrateadequate hematologic, renal, and hepatic function:

RA PV MPA / GPA SLE Absolute neutrophil count (/mm3)

• 1500

• 1500

• 1500

• 1500 Platelets (/mm3)

• 100,000

• 100,000

• 100,000

• 75,000 Hemoglobin (g/dL)

• 9

• 9

• 9

• 8 Creatinine clearance (mL/min/1.73 m2)

• 60

• 60

• 60

• 60 Total serum bilirubin (mg/dL) < 2.5 < 2.5 < 2.5 < 2.5 Liver transaminases (AST/ALT/ALP)

≤ 3x ULN

≤ 3x ULN

• 3x ULN

• 3x ULN Additional Disease-specific Inclusion Criteria Rheumatoid Arthritis

1. Documented diagnosis of RA, meeting the 2010 American College ofRheumatology (ACR)/European League Against Rheumatism (EULAR)classification criteria for RA (Kay, 2012).

2. Have had prior treatment for a period of at least 12 weeks with a biologicdisease-modifying anti-rheumatic drugs (bDMARD e.g., infliximab,rituximab, etanercept, tocilizumab)) and/or a targeted syntheticdisease-modifying anti-rheumatic drugs (tsDMARD e.g., baricitinib,tofacitinib)) and were deemed refractory by either:

3. In the opinion of the Investigator, there was a lack of benefit to atleast two bDMARDs or one bDMARD and one tsDMARDs. Lack of benefit mayinclude inadequate improvement in joint counts, physical function, ordisease activity.

4. Intolerance to at least two lines of prior therapy, including bDMARDsand/or tsDMARDs.

5. Minimum of 6 swollen joint counts (SJC) and 6 tender joint counts (TJC). Pemphigus Vulgaris

6. Confirmed diagnosis of pemphigus vulgaris with active lesions.

7. Positive for anti-desmoglein Dsg1 or Dsg3.

8. Pemphigus Disease Area Index score of > 10%.

9. Subjects will have tried and failed at least 12 weeks of treatment ofimmunosuppressive or biologic standard-of-care agent (methotrexate,azathioprine, mycophenolate mofetil (MMF) or mycophenolic acid (MPA)and corticosteroids, and/or 12 weeks of therapy with IV Gammaglobulin treatments with an exposure of 12 weeks to be consideredresistant/refractory and will be included in this study. Granulomatosis with polyangiitis (GPA) / microscopic polyangiitis (MPA)

10. Clinical diagnosis of granulomatosis with polyangiitis (GPA) ormicroscopic polyangiitis (MPA).

11. Presence of cytoplasmic Antineutrophil cytoplasmic antibody (c-ANCA)or proteinase-3 (PR3-ANCA) or myeloperoxidase ANCA (MPO-ANCA)

12. Have ≥ 1 "major" item, or ≥ 3 "other" items, or ≥ 2 renal items onthe Birmingham Vasculitis Activity Score Version 3 (BVASv3).

13. For GPA/MPA, subjects will have tried and failed at least 12 weeks oftreatment of immunosuppressive (Cyclophosphamide, mycophenolatemofetil (MMF) or mycophenolic acid (MPA) and corticosteroids), or abiologic standard-of-care agent such as Rituximab will be included inthis study. Systemic Lupus Erythematous

14. Diagnosis of SLE according to the 2019 European League AgainstRheumatism/American College of Rheumatology (EULAR/ACR)Classification Criteria.

15. Total systemic lupus erythematosus disease activity index (SLEDAI-2K) ≥ 8 at screening excluding alopecia, mucosal ulcers, and fever.

16. Positive for anti-double-stranded deoxyribonucleic acid (dsDNA)antibodies.

17. For SLE, subjects will have tried and failed at least 12 weeks of 2conventional therapies which, at the discretion of the investigator,includes antimalarials, corticosteroids, immunosuppressive agents,such as mycophenolate mofetil, Methotrexate, Azathioprine, as well asbiologic agents such as Belimumab, Anifrolumab, and Rituximab. The following criteria for standard-of-care therapies must be met:

18. If receiving antimalarial drugs (e.g., hydroxychloroquine, chloroquine,quinacrine), must have used the medication for ≥ 12 weeks prior to firststudy treatment and at a stable dose for a minimum of 6 weeks prior tofirst administration of AB-101.

19. If receiving immunomodulatory drugs (mycophenolate mofetil [MMF]/mycophenolic acid ≤ 2 g/day, azathioprine/6 mercaptopurine (AZA/6MP) ≤ 2 mg/kg/day, leflunomide ≤ 40 mg/day, methotrexate (MTX) ≤ 25 mg/wkwith concomitant folic acid [recommend ≥ 5 mg/wk]), calcineurin inhibitor,and/or cyclosporin A, receiving a stable dose for at least 12 weeks priorto the first administration of AB-101. Oral corticosteroid (OCS) <20 mg/day prednisone or equivalent started atleast 12 weeks prior to first study treatment and at a stable dose for atleast 4 weeks prior to first administration of study treatment. It must beplanned that the background standard-of-care treatment remains at a stabledose throughout the Screening Period.

Exclusion Criteria: General Exclusion Criteria (applicable to subjects in all 4 studiedindications) 1. Subjects who received Cyclophosphamide within 3 months 2.Laboratory values outside the protocol-defined range at screening, unlessthe PI documents that the abnormal laboratory value does not compromisepatient safety or interfere with the study's goals. 3. Known hypersensitivity or contraindication to any drug products orany component of the drug products they plan to receive (e.g.,cyclophosphamide, fludarabine, rituximab, AB-101). 4. History of an anaphylactic reaction to parenteral administration ofcontrast agents, human or murine proteins or monoclonal antibodies orDMSO (Dimethyl sulfoxide). 5. Prior treatment with any B-cell targeted therapy within 3 months ofthe start of the planned lymphodepletion regimen (e.g., rituximab orother anti-CD20, anti-CD19, anti-CD22 monoclonal antibodies) 6. Priortreatment with any autologous or allogeneic cell therapy approachusing genetically modified immune cells (e.g., T, NK, macrophages, orgamma-delta T cells modified with chimeric antigen receptors (CAR)). 7. Received any of the following within 6 months of the start of theplanned lymphodepletion regimen:

1. Immunoglobulin replacement therapies (IV or SC)
2. Plasmapheresis. 8. History of a major organ transplant (e.g., heart, lung,kidney, liver) or hematopoietic stem cell/marrow transplant, or are due toreceive such transplantation.
3. Known past or current malignancy except for cervical carcinoma ofstage 1B or less, noninvasive basal cell or squamous cell skincarcinoma, Noninvasive, superficial bladder cancer, Prostate cancerwith a current prostate specific antigen (PSA) level < 0.1 ng/m, Anycurable cancer with a complete response duration of > 2 years 10. Anyhistory of a B cell malignancy, even if subjects have achieved acomplete response.
4. Known clinically significant cardiac disease: Within the prior 6months of signing the informed consent form, onset of unstable anginapectoris or acute myocardial infarction; congestive heart failure (grade III or IV as classified by the New York Heart Association),pericarditis present during screening or at baseline, heartrate-corrected QT interval (QTcF) prolongation > 470 msec atscreening, unless secondary to stable conduction disorders (e.g.,left bundle-branch block) 12. Unresolved toxicities from priortherapy, defined as having not resolved to Grade ≤ 1, or to thelevels dictated in the eligibility criteria.
5. Have clinical evidence of significant unstable or uncontrolled acuteor chronic diseases not due to RA, PV, GPA/MPA, SLE (e.g.,cardiovascular, pulmonary, hematologic, gastrointestinal, hepatic,renal, neurological, malignancy, or infectious diseases) which, inthe opinion of the principal investigator, could confound the resultsof the study or put the subject at undue risk.
6. Have a planned surgical procedure or a history of any other medicaldisease (e.g., cardiopulmonary), laboratory abnormality, or condition (e.g., poor venous access) that, in the opinion of the principalinvestigator, makes the subject unsuitable for the study.
7. Have any signs or symptoms of illness/infection or have received anyvaccinations (live or inactivated) within 6 weeks of Day 1.
8. Have current drug or alcohol abuse or dependence, or a history ofdrug or alcohol abuse or dependence within ≤ 1 year prior to Day 1.
9. Human immunodeficiency virus (HIV) infection, based on laboratorytesting performed during the screening period.
10. Currently pregnant or lactating (breast feeding must not be startedwithin 6 months of the last dose of AB-101).
11. Any other considerations that might interfere with the assessment ofsafety or efficacy, or that the investigator deems inappropriate forinclusion.
12. Any medical, psychological, familial, or sociological condition that,in the Investigator's opinion, would impair the subject's ability toreceive study treatment or comply with study requirements.
13. Severe disease progression or health deterioration within 2 weeks ofDay 1 that, in the opinion of the Investigator, could impair theability of the subject to receive study treatment or comply withstudy requirements.
14. Known past or current clinically significant lung disease. 23.History of, or current, chronic pulmonary disease (e.g., COPD,asthma, etc.) not meeting DLCO and FEV1 eligibility criteria 24.Pulmonary manifestations of underlying autoimmune disease that maycompromise pulmonary function.
15. History of tobacco exposure of ≥ 5 pack years 26. Subjects with aprior history of hypogammaglobulinemia or with low IgG levels (< 600mg/dL). Subjects who have received Intravenous Immunoglobulins (IVIG)for any reason in the 3 months prior to screening will be excluded.
16. Current use of tobacco product Additional Disease specific ExclusionCriteria Rheumatoid Arthritis
17. History of a rheumatologic autoimmune disease other than RA (exceptsecondary Sjögren's)
18. Significant systemic involvement secondary to RA (e.g., vasculitis,pulmonary fibrosis, Felty's syndrome)
19. Other arthritis, including Juvenile idiopathic arthritis (JIA) oridiopathic arthritis diagnosed before the age of 16 years; PsoriaticArthritis; Axial spondylarthritis or any other disease associatedwith inflammatory arthritis; Active fibromyalgia with pain symptomsor signs that would interfere with clinical assessments for RA. Pemphigus Vulgaris
20. Any condition, including potential flares or new infected ornon-infected lesions that would, in the investigator's judgment,interfere with full participation in the study. Granulomatosis with polyangiitis (GPA) / microscopic polyangiitis (MPA) 1.Any other multi-system autoimmune disease. 2. Have required significantongoing management of infections Systemic Lupus Erythematous
21. Drug-induced lupus.
22. Participants with a history of severe anti-phospholipid syndrome.