AnaptysBio Reports Positive Topline Data from GALLOP Phase 2 Clinical Trial of Imsidolimab in Moderate-to-Severe Generalized Pustular Psoriasis (GPP) - Seite 2

Study Data
Key data available to date from the 8 patients enrolled in the GALLOP trial are as follows:

• Mean baseline value on the modified Japanese Dermatology Association severity index total score (mJDA-SI) was 9 (Table 1), body surface area covered by erythema and pustules was 24% and the serum C-reactive protein (CRP) was 56 mg/L. Patients were on average 51 years of age, 50% female and diagnosed with GPP for 4.3 years.
• Six of 8 (75%) patients treated with imsidolimab monotherapy achieved the primary endpoint of improvement in the CGI scale on Day 29. Two of 8 (25%) patients were considered to have not met the primary endpoint because they dropped out of the trial prior to Day 29.  
• mJDA-SI score, which incorporates both dermatological and systemic aspects of GPP, decreased on average by 29% on Day 8 and 54% on Day 29. Erythema with skin pustules, which clinically defines GPP, decreased by 60% on Day 8 and 94% on Day 29. Serum CRP, which is an indicator of systemic inflammation, was normal (less than 5 mg/L) for 5 of the 6 patients achieving the primary endpoint on Day 29.     
• Genotypic testing indicated homozygous wild-type IL-36RN, CARD14 and AP1S3 alleles for all 8 patients. We believe this suggests that imsidolimab is broadly applicable to pustular diseases irrespective of genetic drivers.
• Anti-drug antibodies were not detected as of Day 29 in any patient.
  

Endpoint	Baseline		Day 8 Relative to Baseline		Day 29 Relative to Baseline
Improvement on CGI	N/A		7 of 8 patients		6 of 8 patients
mJDA-SI	9		-29%		-54%
Erythema with Skin Pustules (% body surface area)	24%		-60%		-94%

Table 1. Key endpoints at Day 8 and Day 29 relative to baseline.

Imsidolimab was generally well-tolerated and most treatment-emergent adverse events were mild to moderate in severity and resolved without sequelae. No infusion or injection site reactions were observed. One patient dropped out of the trial due to a diagnosis of Staphylococcal aureus bacteremia in the first week, which was a serious adverse event deemed to be possibly drug-related. Because the patient was symptomatic prior to dosing and had a prior medical history of bacteremia, a common comorbidity of GPP, the Company does not believe this event is likely attributable to imsidolimab. Another patient dropped out of the study on Day 22 due to investigator reported inadequate efficacy. One patient contracted COVID-19 during the course of the trial, which was mild, unrelated to imsidolimab, and did not lead to study discontinuation.