Efficacy and Safety Study of BCX7353 as an Oral Treatment for the Prevention of Attacks in HAE

Treatment comparisons between each berotralstat dose and placebo in the rate of investigator-confirmed HAE attacks during the Part 1 dosing period were analyzed using a negative binomial model. The number of investigator-confirmed attacks was included as the dependent variable, the treatment was included as a fixed effect, the stratification variable (baseline attack rate) was included as a covariate, and the logarithm of duration on treatment was included as an offset variable. The estimated attack rate for each treatment group, the treatment differences expressed as the attack rate ratio (berotralstat over placebo rate ratio), and the associated 95% confidence intervals (CIs) were provided from the negative binomial model.

The safety data was assessed for the safety population, for subjects who entered Part 2 and Part 3, and includes TEAEs that began in Part 2 or 3, respectively, for these subjects. Safety data for Part 2 and Part 3 is combined to clearly show TEAEs occurring in subjects as the proceeded through the 2 study parts. TEAEs are defined as AEs that occurred on or after first dose of study treatment, whether in Part 1 or 2, and were assigned to the relevant treatment depending on when the TEAE began (Part 2 or Part 3 treatment). No statistical analysis was performed on this safety data.

Change in Quality of Life, on a 1-100 scale, where higher scores indicate more impairment and a decrease (change with a negative value) in AE-QoL questionnaire scores indicates an improvement in the subject's QoL. The minimum clinically important difference (MCID) for the AE-QoL questionnaire is -6 (total score). The AE-QoL is only validated for adults; however, data were collected on all adult and adolescent study subjects.

Assessment of proportion of days subjects had angioedema symptoms from expert-confirmed HAE attacks during Part 1.

The rate of expert-confirmed HAE attacks for the effective treatment period gives an analysis of the efficacy of active treatment after berotralstat had reached steady-state concentrations, given the effective half-life of 150 mg berotralstat in Study BCX7353-106 (Study 106) of 89 hours.

Monthly Attack Rate was defined as the total number of investigator-confirmed HAE attacks experienced during the treatment period adjusted for the length of a month (defined as 28 days) and the number of days the subject was on treatment during that month. The end of Month 6 was defined as the start of Part 2 treatment.

Baseline investigator-confirmed attack rate was defined as the total number of investigator-confirmed HAE attacks experienced in the period between screening and first dose of study drug adjusted for the length of a month (defined as 28 days) and the number of days during that period.

Angioedema-specific QoL was assessed by the AE-QoL, consisting of 4 domains (i.e., functioning, fatigue/mood, fears/shame, and nutrition) and a total score. The AE-QoL scores range from 0 points (best QoL) to 100 points (worst QoL). A decrease (change with a negative value) in AE-QoL questionnaire scores indicates an improvement in the subject's QoL. The minimum clinically important difference (MCID) for the AE-QoL questionnaire is -6 (total score). The AE-QoL was completed by the subjects at each visit starting at baseline, and questions were answered with regard to the previous 28 days. For subjects who received active treatment following placebo, visits were adjusted according to the date of the first dose of active treatment.

The Treatment Satisfaction Questionnaire for Medication (TSQM) was completed by subjects at baseline and at each study visit until the end of the study. TSQM scores consisted of 14 items of which 13 items were made up of 3 specific scales (Effectiveness, Side Effects, and Convenience) and 1 global satisfaction scale (Global Satisfaction). At baseline, TSQM questionnaires were completed based on subject's satisfaction with usual medications. At all other time points for collection of TSQM, subjects were asked about their level of satisfaction or dissatisfaction with the study drug. Scales scores were calculated for each scale and were transformed into scores ranging from 0 to 100, with higher scores indicating higher satisfaction. TSQM score and corresponding change from baseline values were calculated at each visit. For subjects who received active treatment following placebo, visits were adjusted according to the date of the first dose of active treatment.