Background: The optimal management for immune related adverse events (irAEs) in patients who do not respond or become intolerant to steroids is unclear. Guidelines suggest additional immunosuppressants based on case reports and expert opinion. Methods: We examined patients with advanced lung cancers at MSK treated with immune checkpoint blockade (ICB) from 2011-2020. Pharmacy records were queried to identify patients who received systemic steroids as well as an additional immunosuppressant (eg TNFα inhibitor, mycophenolate mofetil). Patient records were manually reviewed to examine baseline characteristics, management, and outcomes. Results: Among 2,750 patients with lung cancers treated with ICB, 51 (2%) received both steroids and an additional immunosuppressant for a severe irAE (TNFα inhibitor (73%), mycophenolate mofetil (20%)). The most common events were colitis (53%), pneumonitis (20%), hepatitis (12%), and neuromuscular (10%). At 90 days after start of an additional immunosuppressant, 57% were improved from their irAE, 18% were unchanged, and 25% were deceased. Improvement was more common in hepatitis (5/6) and colitis (18/27) but less common in neuromuscular (1/5) and pneumonitis (3/10). All patients with hepatitis received mycophenolate mofetil 500-1000mg BID for a median of 3 months, range 2-5 months. Of the 18 patients with colitis who improved with a TNFα inhibitor, 10 needed just one dose. Of 13 patients who died, 4 were related to toxicity from immunosuppression (3, infection-related deaths; 1, drug-induced liver injury leading to acute liver failure). Those who died from immunosuppressive therapy received higher amounts of systemic steroids than those who did not (max median 525 vs 132 mg prednisone equivalent, Mann Whitney U p = 0.004, total median 5.9k vs 2.3k mg prednisone equivalent, p = 0.004). Of 31 patients who received at least 3 weeks of prednisone ≥ 20mg, most (90%, 28/31) had at least one side effect that was brought to clinical attention (most commonly altered mood/ sleep, 52%, increase in BMI > 1kg/m2, 45%, and infection, 32%). Conclusions: Steroid-refractory/resistant immune related adverse events are rare. While existing treatments help patients with hepatitis and colitis, most patients with other irAEs remain refractory and/or experience toxicities from immunosuppression. Systemic steroid use likely contributed to side effects and mortality. A more precise understanding of the pathophysiology of specific irAEs is needed to guide biologically informed treatment regimens for severe irAEs to realize the true benefit of ICB therapy.