4D Molecular Therapeutics, Inc. announced updated interim safety and efficacy data on six adults with Fabry disease cardiomyopathy treated with a single intravenous (IV) infusion of 4D-310 (1E13 vg/kg) with follow-up of 12-33 months overall, including 12-24 month follow-up data on cardiac contractility, exercise capacity, quality of life and cardiac biopsy data. The data was presented in a late-breaking session at WORLDSymposium? 2024 in San Diego, California on Friday, February 9, 2024.

INGLAXA Phase 1/2 Clinical Trial Design & Enrollment: Dose escalation and dose expansion trial assessing a single IV infusion of 4D-310 in a broad and diverse Fabry disease patient population Enrolled six patients, each treated with 1E13 vg/kg of 4D-310 and a prophylactic corticosteroid immunosuppressive regimen; Protocol amended to change immunosuppressive regimen to rituximab and sirolimus (enrollment on this amendment pending); Cardiac biopsies allowed at week 6 and 26 in the INGLAXA-2 trial (to date, one patient had biopsies performed). INGLAXA Phase 1/2 Interim Data Summary (Data Cutoff: December 5, 2023): Safety and Tolerability: Previously reported cases of aHUS (n=3) have fully resolved; No clinically significant cardiac or liver toxicities; No new 4D-310?related adverse events > Grade 1 since the last interim update in February 2023. Echocardiography Contractility Assessments (Global Longitudinal Strain, GLS): Improved GLS in all five evaluable patients by month 12; Two patients who reached 24 months of follow-up both showed clinically meaningful improvement with change from baseline exceeding the minimal detectable difference of -1.5% (-2.8 and -2.9%, respectively); Cardiopulmonary Exercise Testing (CPET) Peak VO2 Assessments.

3 of 4 evaluable patients demonstrated clinically meaningful improvement by CPET peak VO2 with change from baseline exceeding the minimal clinically important difference (MCID) of +1.5 at month 12 (+1.8, +2.0 & +7.0); One patient who reached 24 months of follow up continued to show meaningful improvement with change from baseline exceeding the MCID of +1.5 (+7.8). Cardiac Quality of Life Assessments (Kansas City Cardiomyopathy Questionnaire): Two patients had low baseline scores <90 (scale 0-100); both patients had clinically meaningful improvements in QOL (exceeding the MCID of +5); One patient had 12 months follow-up: Clinical & Overall Summary Scores improved by +5.7 and +11.7, respectively; One patient had 24 months follow-up: Clinical & Overall Summary Scores improved by +12.5 and +8.3, respectively; Three patients had baseline values >90 (92.7, 100 & 100); all remained stable through 12-24 months (+1.1 to -1.6). Cardiac Biopsy Assessments of Transgene Expression and Substrate Clearance: Cardiac biopsies at week 6 and 26 from one patient showed robust & durable 4D-310?mediated transgene expression in cardiomyocytes; All samples positive for transgene RNA (ISH) & AGA protein (IHC); At week 26, mean Gb3 inclusion body volume per cardiomyocyte was reduced 15% from week 6 and 61% vs.

historical sample collected approximately 7 years prior to enrollment and analyzed independently by investigator. Next Steps for Development of 4D-310: FDA submission of data from the NHP study evaluating the safety and biodistribution of IV 4D-310 with the R/S immunosuppressive regimen compared to the prior prednisone regimen expected in Second Quarter 2024.