Sell Rating for GlaxoSmithKline Due to Limited Growth Prospects for Blenrep Amid Competitive Challenges and Regulatory HurdlesWe forecast peak Blenrep sales of ~£600m in the R/R multiple myeloma setting and ascribe limited to no sales for earlier line use (DREAMM-10 trial). the front line (DREAMM-10) setting continues, though trial design uncertainty remains (data expected in 2031). The ongoing front-line trial (DREAMM-10) could face similar issues to later line trials given: (1) potential under-dosing, utilising the 1.9mg/kg dose every 8 weeks, then 12 weeks. While 1.9mg /kg was used as the maintenance dose in the DREAMM-8 trial, it was noted in the ODAC that there was an efficacy loss, without a noticeable safety gain. Importantly, the interval between doses has been extended to 8-12 weeks (vs 4 weeks in DREAMM-8), which again, could be detrimental to efficacy. (2) Uncertainty around sufficient US enrolment.