Background: High grade immune-related adverse events (irAEs) to cancer immune checkpoint inhibitors (ICI) require considerable immunosuppression (IS) with high-dose steroids and steroid-sparing IS (SSIS) for steroid-dependent cases. T lymphocyte-specific IS has generally been avoided or used with significant caution due to the fear that these agents may negatively impact ICI efficacy. We sought to determine whether T cell-specific IS agents, such as calcineurin inhibitors (CNIs), have an adverse effect on tumor control when compared to other immunomodulatory drugs (IMDs). Methods: We retrospectively analyzed clinical annotations of adult patients treated with ICIs for malignancy from 1/1/2000-12/31/2019, highlighting patients who were managed with SSIS, specifically those most commonly used for autoimmune disease therapy. Topical IS use was excluded. Patients were categorized as tumor responders or non-responders, and irAEs were graded according to National Cancer Institute’s Common Terminology Criteria for Adverse Events (CTCAE). Progression-free survival (PFS) was assessed via Kaplan-Meier curve. Results: 1331 unique individuals were prescribed ≥1 ICIs, with 526 prescribed systemic steroids (39.5%) and 90 (6.8%) patients prescribed SSIS agents, 25 patients with >1 SSIS: mycophenolate (39), methotrexate (26), leflunomide (5), azathioprine (3), rituximab (24), tocilizumab (3), infliximab (8), etanercept (1), adalimumab (1), golimumab (1) and CNIs (18): cyclosporine, tacrolimus. IMDs hydroxychloroquine (6) and sulfasalazine (5) were also prescribed. The objective response rate was 50.0% in the CNI group compared to 45.5% in the IMD cohort and 45.4% in the irAE group (CTCAE grade matched) with steroids alone without any SSIS. Median PFS were compared between CNI cohort (5.4 months, range 1.3-34 months) to IMD (1.1 months, range 0.4-6.4, p=0.02) and steroid alone (2.4 months, range 0.69-17.7, p=0.48). Multiple regression analysis identified irAE presence as an independent correlates to tumor response (p=0.02). Conclusions: T cell-specific IS should not be excluded from irAE treatment algorithm as we observed that PFS was comparable to immunomodulators and similar efficacy was observed compared to steroids alone. Rapid identification and management of irAEs can help mitigate morbidity but there are virtually no reliable clinical trials to guide irAE management with SSIS. These findings support the need for larger, prospective evaluation of immunosuppression use for high grade irAE therapy.