The clinical evidence for linzagolix came from 2 randomised controlled trials, PRIMROSE 1 and 2, which compared linzagolix with placebo. The trials were very similar in structure, inclusion and exclusion criteria, and the outcomes measured. The company explained that because of the similarity of these trials, it was appropriate to give pooled efficacy data up to week 24. The primary outcome for both trials was attainment of response, which was a reduction in HMB defined as menstrual blood loss (MBL) of less than or equal to 80 ml and a greater than or equal to 50% reduction in MBL from baseline. Secondary outcomes included percentage change from baseline in MBL, fibroid volume and uterine volume, pain, percentage change from baseline in haemoglobin in people with anaemia and change in quality of life (uterine fibroids severity and quality of life [UFS‑QoL] and EQ‑5D‑5L instruments). Four different regimens of linzagolix and placebo were compared. The regimens assessed were 100 mg and 200 mg of linzagolix both with and without hormonal ABT. People having any linzagolix dosing regimen were significantly more likely to have a response than placebo. The greatest effect compared with placebo was seen with the 200 mg with hormonal ABT regimen, pooled analysis odds ratio (OR) 10.77 (95% confidence interval [CI] 6.66 to 17.42). The 100 mg without hormonal ABT regimen had the lowest response effect compared with placebo, pooled analysis OR 2.75 (95%CI 1.82 to 4.16), and the remaining regimens, 100 mg plus hormonal ABT and 200 mg without hormonal ABT, had results between these. The committee noted that there appeared to be a placebo effect for the response outcome because 66 people (32%) in the placebo group reported having a reduction in HMB in the pooled PRIMROSE results. The company explained that, in the PRIMROSE trials, MBL was measured using returned used sanitary products, and if no products were returned this was considered in the trial to mean there was no bleeding for that day. If people were unable to return sanitary products on the days of menstrual blood loss for any reason, then this may have overestimated the reduction in MBL. The company considered that the return of these products would be particularly burdensome in the placebo group, where there was heavier bleeding, and assume that this could have caused or contributed to the placebo effect. The EAG acknowledged this explanation but considered that it was speculative and that there could be other reasons for the placebo effect, such as regression to the mean. For the secondary outcomes, all linzagolix regimens were significantly better than placebo with the exception of change from baseline in primary uterine fibroid volume and uterine volume outcomes for the 100 mg plus hormonal ABT regimen, and the EQ-5D-5L outcome. The committee noted that the 2 trials returned slightly different results with linzagolix appearing slightly more effective for some outcomes in PRIMROSE 2 than PRIMROSE 1. The EAG noted that this might reflect differences in the geographical and ethnic composition of the trial populations, but that this was uncertain. The committee concluded that linzagolix was more effective than placebo at treating moderate to severe symptoms of uterine fibroids.