The NCI 9673 trial demonstrated that adding the CTLA-4 inhibitor ipilimumab to the PD-1 inhibitor nivolumab did not improve response rate, PFS, or overall survival in patients with previously treated anal cancer. This finding discourages this combination approach, avoiding unnecessary toxicity.

The HER2CLIMB-02 trial found that adding tucatinib to TDM-1 offered only a modest 2-month PFS benefit. This came at the cost of substantially increased toxicity, including transaminitis and diarrhea, suggesting the two agents are better used sequentially for most patients.

An ADC may show better response rates than chemotherapy, but its true benefit is compromised if toxicities lead to treatment discontinuation. As seen with failed PARP/IO combinations, if patients cannot tolerate a drug long enough, the regimen's overall effectiveness can become inferior to standard therapy.

While the feared side effect of severe lung inflammation (pneumonitis) did not increase, other immune-mediated adverse events did. This led to higher rates of treatment discontinuation in the experimental arm, potentially negating any benefits of the concurrent approach and contributing to the trial's failure.

Despite the individual high efficacy of both BCMA-directed therapies and anti-CD38 antibodies, there is significant clinical concern about combining them. The potential for compounded immunosuppression and severe infection risk is a major barrier shaping clinical trial design and favoring sequential use over concurrent combination.

Contrary to the assumption that two drugs are always more toxic than one, the Lenvatinib-Belzutifan combination in the LightSpark-011 trial presented a different, but not quantifiably worse, toxicity profile compared to cabozantinib monotherapy, challenging conventional thinking on combination therapy side effects.

In solid tumor immunotherapy, significant efficacy gains almost always correlate with increased toxicity. This study's claim of nearly doubled progression-free survival with identical toxicity rates is biologically implausible and was a primary reason for skepticism, even before analyzing the trial's methodology.

The TRILINX trial revealed Xevinapant's toxicity was so high that it forced reductions in standard, effective treatments like cisplatin and radiation. This compromised the foundational therapy, leading to worse patient outcomes and demonstrating a key risk in adding novel agents to established regimens.

While the avutometanib/defactinib combination is newly approved for KRAS-mutated ovarian cancer, its significant toxicity profile—causing up to a third of patients to stop treatment—creates a clear clinical need for agents like specific KRAS inhibitors that may offer similar efficacy with better tolerability.