OBJECTIVES: The purpose of this study was to develop an early economic model to compare the maximum supported cost-effective prices (CEP) of recently launched co-administered branded products to their list prices in the UK. METHODS: An early economic model was constructed in Microsoft Excel using a three-state partitioned-survival approach. A pragmatic literature search was performed identified three co-administered branded therapies as case studies: pertuzumab + trastuzumab(+docetaxel) in HER2+ breast cancer, trametinib + dabrafenib in melanoma, and idelalisib + rituximab in chronic lymphocytic leukaemia; all therapies except rituximab were dosed to progression. Progression-free and overall survival for the intervention and comparator arms were sourced from relevant clinical trials; survival was assumed to follow an exponential distribution. Representative acquisition, administration, and monitoring costs were sourced from the literature and health technology assessment appraisals. The maximum CEP for each analogue was evaluated at two different willingness-to-pay (WTP) thresholds: £20,000/QALY and £50,000/QALY. All costs and outcomes were discounted at 3.5%. RESULTS: The results from the early economic model suggested that neither pertuzumab nor trametinib would ever be a cost-effective therapy even at a WTP threshold of £50,000. However, at both WTP thresholds of £20,000 and £50,000/QALY, idelalisib was projected to have a cost-effective price, which was similar to the current list price in the UK. CONCLUSIONS: These results demonstrate that neither pertuzumab nor trametinib have CEPs, while the CEP for idelalisib is similar to the UK launch price, demonstrating that add-on branded therapies co-administered without anchors dosed to progression (here, rituximab) will permit higher prices while remaining cost-effective.  This analysis highlights the utility of early economic models in evaluating potential pricing and HTA barriers early in the development process.