Background: Pembrolizumab is a PDL1 inhibitor licensed for the treatment of unresectable melanoma at a dose of 2mgkg every three eeks. A population pharmacokinetic model based on to compartment first order elimination model has been used to describe the pharmacokinetics of pembrolizumab in advanced malignancies. Dose banding or the standardisation of doses into a defined set of ranges offers an alternative approach to precise dosing. The aim of this ork is to evaluate using a simulated study and data from 43 patients treated at one UK centre the change in cost, drug exposure and target engagement beteen precise dosing  2mgkg , banded and fixed dosing  150mg and 200mg  strategies. Methods: Data from 43 consecutive patients ho received pembrolizumab ith a median eight of 79.5kg  range 44-130kg . 5 cycles of treatment based on median time on treatment of Keynote-002 trial as assumed for cost evaluation. 1000 random individuals ere evaluated in a simulated study for pharmacokinetic and pharmacodynamic assessment. The published population PK model ere used to simulate change in exposure and probability of achieving reported trough level  10mgL  required for maximum target engagement for different dosing strategies. Results: Based on 43 patients receiving 5 cycles of pembrolizumab, the costs of different strategies are illustrated in Table 1. The table also includes simulated area under the curve and mean probability of achieving a trough level of 10mgL required for maximum target engagement before the second cycle of treatment for the different dosing strategies. Conclusions: Significant cost reduction can be achieved by banded and fixed dose strategies compared to precise dosing strategy hile maintaining comparable level of exposure and target engagement. PembrolizumabDrug Cost of 5 cyclesx2A; xA3;  n=43 Relative Drug Cost Saving  percent  n=43 Simulated AUCMean mg.dayL SD Mean prob of Target EngagementPrecise  2mgkg 1,699,11101359 375 0.51Dose Band  10 percent variance 1,518,825 1,462,937 ith vial sharing 10.6 13.9 ith vial sharing 1356 359 0.51Fixed dose  150mg 848,175501384 405 0.53Fixed dose  200mg 1,130,900331846 540 0.86ltfn id=TF-168319-001-1 ltp class=mtgabstract-table-fn x2A;United Kingdom costlttable-rap-foot ,J Clin Oncol 34, 2016  suppl; abstr 9547 00:00.0,MelanomaSkin Cancers