Phase 2, Parallel Group, Rollover Study of AKR-501 in Patients With ChronicITP Who Completed 28 Days of Study Treatment in Protocol 501-CL-003

A TEAE was defined as 1) the AE started on or after the date of first dose of study drug up to and including 30 days after the last dose of study drug, or 2) the AE started before the first dose of study drug but worsened in severity on or after the date of first dose of study drug up to and including 3 days after the last dose of study drug. For participants having a tapering period of study drug, the last dose day is the last day of study drug during the tapering period. Related AEs included those whose relationship was categorized as possible or probably by the investigator. Dose interruption includes dose decreased, dose previously stopped, permanently stopped, or temporarily stopped. The safety population was divided into three subgroups based on the mean daily dose of active study drug taken; lower 1/3 (less than 8.85 mg avatrombopag), middle 1/3 (greater than or equal to 8.85 mg but less than 13.5 mg avatrombopag), and upper 1/3 (greater than or equal to 13.5 mg avatrombopag).

A TEAE was defined as 1) the AE started on or after the date of first dose of study drug up to and including 30 days after the last dose of drug, or 2) the AE started before the first dose of study drug but worsened in severity on or after the date of first dose of study drug up to and including 3 days after the last dose of study drug. For participants having a tapering period of study drug, the last dose day is the last day of study drug during the tapering period. The safety population was divided into three subgroups based on the mean daily dose of active study drug taken; lower 1/3 (less than 8.85 mg avatrombopag), middle 1/3 (greater than or equal to 8.85 mg but less than 13.5 mg avatrombopag), and upper 1/3 (greater than or equal to 13.5 mg avatrombopag).

Drug-related TEAEs included those whose relationship was categorized as possible or probably by the investigator. A TEAE was defined as 1) the AE started on or after the date of first dose of study drug up to and including 30 days after the last dose of drug, or 2) the AE started before the first dose of study drug but worsened in severity on or after the date of first dose of study drug up to and including 3 days after the last dose of study drug. For participants having a tapering period of study drug, the last dose day is the last day of study drug during the tapering period. The safety population was divided into three subgroups based on the mean daily dose of active study drug taken; lower 1/3 (less than 8.85 mg avatrombopag), middle 1/3 (greater than or equal to 8.85 mg but less than 13.5 mg avatrombopag), and upper 1/3 (greater than or equal to 13.5 mg avatrombopag).

Platelet count (PC) was measured from blood draws. Based on avatrombopag response in study 501-CL-003, participants were divided into two subgroups; 1) "Responders", participants who met the primary efficacy response; pretreatment PC was less than 30,000/mm^3 and increased to greater than or equal to 50,000/mm^3 after treatment with avatrombopag, and for participants on steroids, pretreatment PC was greater than or equal to 30,000/mm3 but less than 50,000/mm^3 and increased to a PC greater than or equal to 20,000/mm^3 above their pretreatment values and 2) "Nonresponders", participants who did not meet the primary efficacy response and those who were in the placebo arm. Open-label dose escalation of avatrombopag, as well as reductions in ITP-directed concomitant therapy (e.g. steroids) was allowed for all participants. During the periods of avatrombopag dose escalation and/or ITP-directed concomitant medication reduction, platelet sampling was done weekly.

Platelet count (PC) was measured from blood draws. Based on avatrombopag response in study 501-CL-003, participants were divided into two subgroups; 1) "Responders", participants who met the primary efficacy response; pretreatment PC was less than 30,000/mm^3 and increased to greater than or equal to 50,000/mm^3 after treatment with avatrombopag, and for participants on steroids, pretreatment PC was greater than or equal to 30,000/mm^3 but less than 50,000/mm^3 and increased to a PC greater than or equal to 20,000/mm^3 above their pretreatment values and 2) "Nonresponders", participants who did not meet the primary efficacy response and those who were in the placebo arm. Open-label dose escalation of avatrombopag, as well as reductions in ITP-directed concomitant therapy (e.g. steroids) was allowed for all participants. During the periods of avatrombopag dose escalation and/or ITP-directed concomitant medication reduction, platelet sampling was done weekly.

Platelet count (PC) was measured from blood draws. Based on avatrombopag response in study 501-CL-003, participants were divided into two subgroups; 1) "Responders", participants who met the primary efficacy response; pretreatment PC was less than 30,000/mm^3 and increased to greater than or equal to 50,000/mm^3 after treatment with avatrombopag, and for participants on steroids, pretreatment PC was greater than or equal to 30,000/mm^3 but less than 50,000/mm^3 and increased to a PC greater than or equal to 20,000/mm^3 above their pretreatment values and 2) "Nonresponders", participants who did not meet the primary efficacy response and those who were in the placebo arm. Open-label dose escalation of avatrombopag, as well as reductions in ITP-directed concomitant therapy (e.g. steroids) was allowed for all participants. During the periods of avatrombopag dose escalation and/or ITP-directed concomitant medication reduction, platelet sampling was done weekly.

Platelet count (PC) was measured from blood draws. Based on avatrombopag response in study 501-CL-003, participants were divided into two subgroups; 1) "Responders", participants who met the primary efficacy response; pretreatment PC was less than 30,000/mm^3 and increased to greater than or equal to 50,000/mm^3 after treatment with avatrombopag, and for participants on steroids, pretreatment PC was greater than or equal to 30,000/mm^3 but less than 50,000/mm^3 and increased to a PC greater than or equal to 20,000/mm^3 above their pretreatment values and 2) "Nonresponders", participants who did not meet the primary efficacy response and those who were in the placebo arm. Open-label dose escalation of avatrombopag, as well as reductions in ITP-directed concomitant therapy (e.g. steroids) was allowed for all participants. During the periods of avatrombopag dose escalation and/or ITP-directed concomitant medication reduction, platelet sampling was done weekly.

Platelet count (PC) was measured from blood draws. Based on avatrombopag response in study 501-CL-003, participants were divided into two subgroups; 1) "Responders", participants who met the primary efficacy response; pretreatment PC was less than 30,000/mm^3 and increased to greater than or equal to 50,000/mm^3 after treatment with avatrombopag, and for participants on steroids, pretreatment PC was greater than or equal to 30,000/mm^3 but less than 50,000/mm^3 and increased to a PC greater than or equal to 20,000/mm^3 above their pretreatment values and 2) "Nonresponders", participants who did not meet the primary efficacy response and those who were in the placebo arm. Open-label dose escalation of avatrombopag, as well as reductions in ITP-directed concomitant therapy (e.g. steroids) was allowed for all participants. During the periods of avatrombopag dose escalation and/or ITP-directed concomitant medication reduction, platelet sampling was done weekly.

Platelet count (PC) was measured from blood draws. Based on avatrombopag response in study 501-CL-003, participants were divided into two subgroups; 1) "Responders", participants who met the primary efficacy response; pretreatment PC was less than 30,000/mm^3 and increased to greater than or equal to 50,000/mm^3 after treatment with avatrombopag, and for participants on steroids, pretreatment PC was greater than or equal to 30,000/mm^3 but less than 50,000/mm^3 and increased to a PC greater than or equal to 20,000/mm^3 above their pretreatment values and 2) "Nonresponders", participants who did not meet the primary efficacy response and those who were in the placebo arm. Open-label dose escalation of avatrombopag, as well as reductions in ITP-directed concomitant therapy (e.g. steroids) was allowed for all participants. During the periods of avatrombopag dose escalation and/or ITP-directed concomitant medication reduction, platelet sampling was done weekly.

A participant who used steroids at study entry was considered to have permanently discontinued steroid use if they had no steroid use during the last 8 weeks of the study Treatment Period. A participant who used steroids at study entry was considered to have decreased concomitant steroid medication by at least 50% if they permanently discontinued steroids, or in no dose of steroid was higher than 50% of their baseline steroid dose during the last 8 weeks of the study Treatment Period.