Patient Disposition and Demographics
A total of 15 patients were included in the Volume Cohort, 14 of whom completed the study (Fig. 2). One patient discontinued due to an AE at the 25-mL volume level. The Flow Rate Cohort included 18 patients, 17 of whom completed the study. One patient withdrew at the 25-mL/h flow rate level.
The proportion of males and females in the two pump-assisted cohorts was similar (Table 1). Mean (SD) age of these patients was 49.1 (14.2) and 26.7 (24.5) years in the Volume Cohort and Flow Rate Cohort, respectively. Ten patients (55.6%) in the Flow Rate Cohort were ≤ 17 years old (Table 1). Due to the eligibility requirement for patients in the Volume Cohort to have a total weekly IgPro20 dose of ≥ 50 mL, there were no patients aged ≤ 17 years in this cohort, as younger patients would have had a lower body weight, resulting in lower volumes at the same dose in mg/kg. The median BMI was 27.7 kg/m2 in the Volume Cohort and 22.3 kg/m2 in the Flow Rate Cohort; 7 patients (21.2%), 4 in the Volume Cohort and 3 in the Flow Rate Cohort, were considered obese (BMI ≥ 30 kg/m2). Overall, these differences in age and BMI between the cohorts were not considered clinically relevant nor were they anticipated to impact treatment outcomes.
Table 1 Patient demographics and baseline characteristics (safety analysis set) Responder Analysis
In the Volume Cohort, responder rates were 86.7% at the 25-mL volume level and 73.3% at both the 40- and 50-mL/injection site levels, meeting the prespecified success criterion of ≥ 33% for all infusion parameter levels. The percentage of valid infusions before non-response ranged between 85.0 and 100.0% (Fig. 3a). Responder rates at each volume level were similar between non-obese (n = 11; 10 responders [90.9%] at 25 mL; 8 responders [72.7%] at 40 mL and 50 mL) and obese (n = 4; 3 responders [75.0%] at all levels) patients in the Volume Cohort.
In the Flow Rate Cohort, responder rates were 77.8% at 25 and 50 mL/h, 66.7% at 75 mL/h, and 61.1% at 100 mL/h, meeting the prespecified success criterion of ≥ 33% for all infusion parameter levels. The percentage of valid infusions before non-response ranged between 87.1 and 97.9% (Fig. 3b). There were no substantial differences in responder rates at each flow rate level between patients aged ≤ 17 years (n = 10; 80.0% response rate at 25 and 50 mL/h; 70.0% at 75 mL/h; 60% at 100 mL/h) and those aged > 17 years (n = 8; 75.0% at 25 and 50 mL/h; 62.5% at 75 and 100 mL/h). Responder rates in non-obese patients (n = 15) were 86.7% at 25 and 50 mL/h, 73.3% at 75 mL/h, and 66.7% at 100 mL/h; the responder rate was 33.3% (1 responder) at all flow rate levels in obese patients (n = 3).
Effect of High Infusion Parameters on Number of Injection Sites and Infusion Time
In the Volume Cohort, the median weekly number of injection sites decreased from 4 sites at the 25-mL level to 3 sites at the 40-mL and 50-mL levels. Furthermore, the number of patients who used ≥ 4 injection sites per week decreased by 50% (from 8 to 4 patients) from week 1, 25 mL, to week 12, 50 mL (Fig. 4a). Of the 14 patients who completed the study, 9 (64.3%) used fewer injection sites per week at week 12 compared with week 1: 4 patients reduced from 4 to 3 injection sites, 2 patients reduced from 3 to 2 sites, and 3 patients reduced from 2 sites to 1 site. In the Flow Rate Cohort, the mean (SD) weekly infusion time decreased almost fourfold from 47.3 (23.93) min at week 1, 25 mL/h, to 13.1 (7.69) min at week 16, 100 mL/h (Fig. 4b).
Infusion Compliance
In the Volume Cohort, overall infusion compliance was ≥ 90% (Table 2). In the Flow Rate Cohort, 83.3% of patients had infusion compliance ≥ 90%, with < 90% overall compliance reported in 3 patients (Table 2). Of these patients, 1 patient discontinued following 2 infusions at the 25-mL/h level, 1 patient received 3 out of 4 planned infusions at the 50-mL/h level and switched back to 25 mL/h due to poor tolerability, and 1 patient received 2 infusions at the 100-mL/h level and switched back to 75 mL/h due to severe injection site pain. Five patients had a compliance of < 90% at some point during the study (Table 2).
Table 2 Infusion compliance (safety analysis set) Safety and Tolerability
In the Volume Cohort, individual weekly IgPro20 doses ranged from 104.8 to 324.7 mg/kg; median weekly doses for all patients in the cohort ranged from 162.0 to 170.6 mg/kg. In the Flow Rate Cohort, individual weekly IgPro20 doses ranged from 89.5 to 190.5 mg/kg; median weekly doses for all patients in the cohort ranged from 96.7 to 177.0 mg/kg, with median weekly volumes from 10 to 65 mL. Two pediatric patients in this cohort (≤ 17 years category) received very low volumes of 10 mL per week due to low body weight.
Overall, including TEAEs occurring after non-response, 8 patients (53.3%) in the Volume Cohort experienced 25 TEAEs across all infusion flow rates, with a rate of 0.145 TEAEs per infusion. In the Flow Rate Cohort, 12 patients (66.7%) reported 62 TEAEs (0.228 TEAEs per infusion).
Excluding TEAEs occurring after non-response, in the Volume Cohort, 21 TEAEs were reported in 7 patients (46.7%). Of these, 12 TEAEs in 4 patients (26.7%) were deemed related to study drug administration. The overall TEAE rate per infusion was 0.138 (0.079 for related TEAEs) (Table 3). The rate of any TEAE was lower at the 50-mL level compared with the 25- and 40-mL levels, mostly due to the fact that there were no mild TEAEs at the 50-mL level. The rate of moderate TEAEs remained below 0.1 at all infusion levels. No severe TEAEs were reported in this cohort. One treatment-related TEAE (injection site pain) led to discontinuation by 1 patient after completing the 25-mL level (Table 3).
Table 3 Treatment-emergent adverse events under forced upward titration conditions in Pump-Assisted Volume Cohort (safety analysis set)a Excluding TEAEs occurring after non-response, in the Flow Rate Cohort, 48 TEAEs were reported in 12 patients (66.7%). Of these, 35 TEAEs in 8 patients (44.4%) were considered related to the study medication (Table 4). A decrease in the frequency of both mild and moderate TEAEs was observed with increasing infusion flow rate. The overall TEAE rate per infusion was 0.216 (0.158 for related TEAEs) (Table 4).
Table 4 Treatment-emergent adverse events under forced upward titration conditions in Pump-Assisted Flow Rate Cohort (safety analysis set)a The most frequent TEAEs across both cohorts were injection site pain, injection site erythema, and injection site swelling (Table 3 and Table 4). No deaths or serious TEAEs were reported in either cohort (Table 3 and Table 4).
There were no clinically meaningful differences in the frequency, type, or intensity of TEAEs during the study in either cohort. Within the parameters tested in this study, the rate and intensity of TEAEs did not increase with increasing infusion volume or flow rate per injection site.
In the Volume Cohort, tolerability was 100% for all volume levels. In the Flow Rate Cohort, tolerability was 100% for the 25-, 50-, and 75-mL/h flow rates and 98% for the 100-mL/h flow rate. One patient (6 years of age) experienced a severe TEAE (injection site pain) within 72 h after the infusion at the 100-mL/h level, which resolved within a day.
Serum IgG Trough Concentrations
In both cohorts, serum IgG trough levels were similar between day 1 and the end of the study. Mean (SD) IgG levels were 10.19 (2.35) g/L on day 1 and 10.96 (2.42) g/L at the end of the study in the Volume Cohort and 10.40 (2.10) g/L on day 1 and 10.62 (1.87) g/L at the end of the study in the Flow Rate Cohort.