Objective To quantify, compare, and analyse the cradle-to-gate carbon emissions of biologic treatments for severe asthma.

Design Cradle-to-gate carbon emissions for six monoclonal antibody therapies were calculated using MCF Classifier. A representative patient, eligible for all therapies, was defined to enable comparisons. Sensitivity, scenario, and pairwise analyses were conducted to explore variation in emissions and opportunities for reduction.

Outcome Measures The primary outcome was first-year carbon emissions of biologic treatments for a representative patient with severe asthma, expressed in kg CO2e. Additional outcome measures were the effect of varying electricity source on treatment emissions, and the emissions associated with alternative biologic choices.

Results First-year treatment emissions for the representative patient ranged from 1.1 kg CO2e with benralizumab to 188.9 kg CO2e with dupilumab, a 172-fold difference. Variation was driven by the active pharmaceutical ingredient per preparation (30-300 mg). The number of preparations required for first-year treatment (8-52) and the manufacturer’s proportion of non-fossil fuel electricity (NFFE) (22-91%). Sensitivity analysis showed that increasing NFFE to 100% would reduce emissions by 29-90% and the difference between the highest and lowest emission treatments by 91%. Pairwise comparison showed that selecting any biologic instead of dupilumab would reduce emissions by 134-188 kg CO2e per patient-year, equivalent to 340-478 car miles. The emission differences between treatment with benralizumab, mepolizumab, and tezepelumab were minimal.

Conclusions The carbon footprints of biologic treatments for severe asthma vary widely, driven primarily by differences in dose and manufacturer electricity sources. MCF Classifier enabled standardised comparisons between therapies and highlighted opportunities for near-term reduction, including increased use of non-fossil fuel electricity and optimisation of dosing practice. The approach can be applied across other therapeutic areas to support carbon-informed prescribing and healthcare decarbonisation.

Strengths and Limitations of this study

We developed and applied a standardised methodology to estimate cradle-to-gate carbon emissions of biologic treatments for severe asthma, enabling direct comparison across therapies.

A representative patient was used to ensure consistent application of treatment regimens for each therapy.

The methodology relies on secondary data and manufacturer-level disclosures, as product-specific primary data is not available.

The scope was limited to cradle-to-gate emissions, downstream emissions and other components of the clinical pathway were not included.

HT and NR are employees of and own shares in YewMaker. NR is a Non-Executive Director of AstraZeneca. YewMaker received funding from GSK for the application of the methodology to severe asthma. GSK had no role in study design, analysis, interpretation, or manuscript preparation.

The development of the MCF Classifier was funded by YewMaker. The application of methodology to severe asthma biologics was supported by funding from GSK. GSK had no involvement in the study design, execution, analysis, interpretation of data, or in the writing or review of this manuscript.

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