A common clinical observation is that patients who develop significant immune-related toxicities, like colitis or pneumonitis, are frequently the same ones who experience the most profound and durable responses to checkpoint inhibitor therapy.

When combining sacituzumab govitecan (SASE) and pembrolizumab (IO), it's crucial to differentiate the cause of diarrhea. SASE-induced diarrhea is similar to standard chemotherapy, while IO-induced diarrhea often presents with bloody stools and severe abdominal cramping.

The discontinuation rate for pembrolizumab due to side effects was lower in the LITESPARK 022 trial compared to the earlier Keynote 564 trial (20%). This trend suggests that as clinicians gain more experience with immune checkpoint inhibitors, they are becoming more adept at managing immune-related adverse events, allowing more patients to complete their therapy.

The HORIZON-GEA-01 trial for zanidatumab in gastric cancer mandated prophylactic loperamide (4mg BID) for all patients. This was necessary to manage the high rates of diarrhea (up to 80% of patients), a significant GI toxicity associated with the drug's mechanism of action.

New targeted therapies like Zanidatamab and Zolbetuximab show great promise but cause significant side effects like diarrhea and nausea. Their successful clinical adoption hinges on proactive management using detailed guidelines and prophylactic medications, as toxicity can be severe enough to force treatment discontinuation despite the drug's efficacy.

Clinicians can differentiate side effects based on their profile: "-itis" symptoms (colitis, pneumonitis) suggest immunotherapy, while cytopenias and neuropathy point to chemotherapy. Response to steroids is a key diagnostic clue for immune-related events.

When a toxicity like rash occurs with EV+pembrolizumab—which could be caused by either drug—the recommended strategy is to stop both. After the rash improves, reintroduce the drug least suspected of causing it first. If the rash does not recur, it helps confirm the other agent was the culprit.

When patients experience a consistent pattern of diarrhea, clinicians should move from a reactive, per-episode dosing strategy to a proactive, scheduled regimen of loperamide. This provides better control and prevents symptoms from escalating, with the option to de-escalate as the patient stabilizes.

Clinicians should not underestimate Grade 2 diarrhea, which can involve up to six bowel movements above baseline daily. This level of toxicity significantly impacts a patient's daily living and can lead to dehydration and subsequent complications like hyperglycemia, warranting serious monitoring and prompt intervention.