H1 Antihistamine Use Linked to Longer Immunotherapy Duration in Cancer Patients: Study
USA: Patients receiving immune checkpoint inhibitors who were also taking commonly prescribed H1 antihistamines remained on immunotherapy for a significantly longer period than those not using antihistamines, research presented at the 2026 ASCO Annual Meeting has revealed. The findings suggest a potential association between antihistamine use and improved immunotherapy effectiveness across a broad range of solid tumors.
Immune checkpoint inhibitors have revolutionized cancer treatment, but factors influencing their effectiveness remain under investigation. Previous studies have suggested that H1 antihistamines may improve outcomes in patients with lung cancer receiving immunotherapy, though evidence across different cancer types is limited.
To examine this association, Jason Engel and colleagues from the University of Mississippi Medical Center conducted a retrospective analysis of deidentified patient data. The study included 1,182 patients who received at least one cycle of pembrolizumab, nivolumab, or atezolizumab between 2013 and 2025, accounting for 9,878 immunotherapy cycles. Of these, 280 patients were also taking an oral H1 antihistamine, including cetirizine, loratadine, or fexofenadine.
Researchers compared immunotherapy duration, measured by the number of treatment cycles received, between patients treated with immunotherapy alone and those receiving concurrent H1 antihistamines. Statistical analyses were performed using an unpaired two-tailed t-test.
The following were the key findings:
- Patients receiving H1 antihistamines alongside immune checkpoint inhibitors underwent significantly more cycles of immunotherapy than those not using antihistamines.
- The mean number of immunotherapy cycles was 9.9 among H1 antihistamine users compared with 7.9 among non-users.
- H1 antihistamine use was associated with a longer duration of immunotherapy treatment.
- The positive association was particularly evident in patients receiving pembrolizumab.
- No statistically significant association was observed for patients treated with nivolumab.
- No statistically significant association was observed for patients treated with atezolizumab.
- Sex distribution was similar between patients who used H1 antihistamines and those who did not.
- Race was comparable between the two groups.
- Insurance status was also similar between groups, suggesting these factors were unlikely to account for the observed differences.
The researchers concluded that H1 antihistamine use was positively associated with a longer duration of immune checkpoint inhibitor therapy. Because patients generally remain on effective immunotherapy longer, the findings raise the possibility that antihistamines may influence treatment efficacy.
The authors cautioned that the study was retrospective and, therefore, cannot establish a causal relationship. Nevertheless, the results support further investigation into the interaction between antihistamines and cancer immunotherapy. Future studies are planned to assess the effects of H2 antihistamines and to evaluate how concurrent chemotherapy may influence these associations.
The findings were presented as Abstract e24170 in the Journal of Clinical Oncology supplement accompanying the 2026 ASCO Annual Meeting.
Reference:
J Clin Oncol 44, 2026 (suppl 16; abstr e24170). DOI 10.1200/JCO.2026.44.16_suppl.e24170
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