Xolair (Omalizumab) for Treatment of Drug-induced Acute Tubulointerstitial Nephritis (AIN)

Inclusion Criteria: 1. Adult subjects \> 18 years old of both genders 2. Biopsy proven acute interstitial nephritis in the native kidneys without evidence of ischemic or glomerular pathology in the biopsy 3. Normal baseline creatinine defined as estimated GFR ≥ 60 ml/min/SA based on MDRD calculation within 1 year prior to renal biopsy 4. Serum creatinine elevation of \> 0.3 mg/dL and/or doubling of serum creatinine compared to most recent documented creatinine available (at least within the last year) 5. No immunosuppressants in the last three months including prednisone 6. Women of childbearing potential not using the contraception method can be included as this is a one time dosing and has no known long-term effects. Exclusion Criteria: 1. Unwillingness to give consent 2. Patients who are Pregnant (positive serum pregnancy test for females) or breast feeding 3. Documented history of an autoimmune disease 4. Inability or unwillingness to take prednisone for the prescribed duration and/or dose 5. Subjects suspected to have non-drug-induced AIN 6. Subjects not meeting the inclusion criteria 7. Subjects with contraindication to administration of omalizumab 8. Prior use of omalizumab 9. Severe hypersensitivity to omalizumab or any component of the product 10. Known elevated IgE level from other disease processes 11. Subjects taking (nonsteroidal antiinflammatory drug) NSAIDs chronically 12. Use of any other investigational agents in the last 30 days 13. Patients with severe medical condition(s) including metastatic cancer, terminal congestive heart failure, severe ischemic heart disease or any other medical condition in which life expectancy is less than 6 months.