MOIO Trial Raises Survival Concerns With Reduced-Frequency Immunotherapy

Reducing immune checkpoint inhibitor (ICI) administration to every 12 weeks failed to establish progression-free survival (PFS) noninferiority compared with standard dosing in patients with responding advanced or metastatic solid tumors, according to interim findings from the phase 3 MOIO trial (NCT05078047). An overall survival (OS) imbalance raised concerns about the reduced-frequency strategy, without a meaningful improvement in safety.¹

Gwenaëlle Gravis, MD, of Institut Paoli-Calmettes in Marseille, France, presented the findings during the European Society for Medical Oncology (ESMO) Congress 2026 in Madrid. The results do not support implementing this schedule in the studied population, although the interim analyses did not formally establish definitive inferiority.^1,2

Testing Whether Responses Permit Less Treatment

As more patients experience durable responses to immunotherapy, determining how much treatment is necessary has become an important clinical question. Fewer infusions could ease the burden of ongoing care, but a radiographic response alone does not establish that a patient can safely receive less treatment.³

The MOIO protocol drew on evidence that some responses persist after immunotherapy discontinuation and that checkpoint inhibitor target engagement can extend beyond standard dosing intervals. Investigators therefore tested whether reducing treatment intensity could preserve disease control while improving the experience of treatment.⁴

The multicenter, randomized study enrolled 340 patients with locally advanced or metastatic solid tumors who had achieved a partial or complete response after 6 months of standard immunotherapy. Patients continued standard-frequency treatment or received the same ICI dose every 12 weeks. Patients with melanoma in complete response were excluded.^1,2

The trial planned to enroll 646 patients and used a PFS noninferiority margin of 1.30. The protocol also included assessments of quality of life and cost-effectiveness, alongside clinical outcomes.⁴

Survival Findings Raise Concern

At a median follow-up of approximately 18.6 months, the modified intention-to-treat population included 308 patients. Median PFS was 25.0 months with standard dosing and 21.9 months with reduced-frequency dosing (hazard ratio [HR], 1.35; 96.16% CI, 0.90–2.04; 1-sided P = .0635).¹

The prespecified PFS futility threshold was not crossed. Nevertheless, the overall benefit-risk assessment prompted early stopping. Deaths occurred in 10.5% of patients receiving standard treatment and 19.9% receiving reduced-frequency treatment (HR, 2.04; 95% CI, 1.08–3.85; 2-sided P = .0286).¹

These findings require a distinction between an unsuccessful noninferiority assessment and proof that the experimental strategy is inferior. The study did not establish that every 12-week dosing preserved efficacy within the accepted margin. Its early termination and heterogeneous population also limit definitive conclusions about the magnitude of harm.^1,2

For clinical practice, that uncertainty does not provide a basis for adopting the reduced-frequency schedule. The investigators’ institution reported that the survival signal led the independent monitoring committee to recommend early stopping and concluded that the results do not support every 12-week administration in this population.²

No Meaningful Safety Advantage

Grade 3 or 4 immune-related adverse events were reported in 10.5% of patients receiving standard treatment and 9.5% receiving reduced-frequency treatment. Serious adverse events occurred in 26.3% and 25.0%, respectively.¹

The similar rates offered no meaningful safety advantage to offset the survival concerns. They also underscore why fewer administrations should not automatically be interpreted as a less toxic treatment course.

Implications for Oncology Pharmacists

For pharmacists reviewing immunotherapy orders, MOIO highlights the importance of evaluating the dose together with the administration interval. The experimental strategy retained the same dose while extending the time between infusions, thereby reducing treatment intensity.⁴

That approach differs from established dosing alternatives that adjust the dose when extending the interval. For example, FDA-recommended intravenous pembrolizumab schedules include 200 mg every 3 weeks or 400 mg every 6 weeks in applicable settings. MOIO should not be interpreted as evidence against those established options.⁵

When patients ask about fewer visits, pharmacists can explain that maintaining a response after 6 months does not by itself demonstrate that every 12-week dosing will preserve benefit. Discussions should remain specific to the prescribed regimen and the evidence supporting any proposed change.^2,3

Further research remains warranted. The MOIO protocol includes pharmacokinetic and circulating tumor DNA investigations intended to help identify patients suited to reduced treatment intensity. Until such approaches are validated, these findings do not support routine adoption of the schedule tested in MOIO.^2,4

REFERENCES

1. Gravis G, Barthelemy P, Korakis I, et al. MOIO: interim analyses of a phase III randomized non inferiority trial assessing reduced frequency immune checkpoint inhibitors in responding patients with advanced/metastatic cancer. Abstract and oral presentation at: ESMO Congress 2026; October 23-27, 2026; Madrid, Spain. Abstract LBA10. https://cslide.ctimeetingtech.com/esmo2026/attendee/confcal/presentation/list?q=MOIO

2. Institut Paoli-Calmettes. ESMO 2026: l’étude MOIO présentée par la Dre Gwenaëlle Gravis en Presidential Symposium. October 27, 2026. Accessed October 28, 2026. https://www.institutpaolicalmettes.fr/esmo-2026-etude-moio-gwenaelle-gravis/

3. European Society for Medical Oncology. ESMO Congress 2026: what key data will shape the future of oncology? Accessed October 28, 2026. https://www.esmo.org/insights-by-esmo/all-news/esmo-congress-2026-what-key-data-will-shape-the-future-of-oncology

4. Gravis G, Marino P, Olive D, et al. A non-inferiority randomized phase III trial of standard immunotherapy by checkpoint inhibitors vs. reduced dose intensity in responding patients with metastatic cancer: the MOIO protocol study. BMC Cancer. 2023;23(1):393. Published 2023 May 2. doi:10.1186/s12885-023-10881-8

5. FDA. FDA approves pembrolizumab with paclitaxel for platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal carcinoma. February 10, 2026. Accessed October 28, 2026. fda-approves-pembrolizumab-paclitaxel-platinum-resistant-epithelial-ovarian-fallopian-tube-or