**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Hendrea S.A. Tingen, department of Nuclear Medicine and Molecular Imaging, University Medical Centre Groningen, Groningen, The Netherlands

**Main Body of the Abstract**
Introduction: Patisiran, a small interfering RNA, improves neuropathy and cardiac parameters in hereditary ATTR (ATTRv) amyloidosis. Reductions in extracellular volume by cardiac magnetic resonance imaging and cardiac tracer uptake on bone scintigraphy in patients receiving patisiran suggest amyloid regression. However, evidence confirming amyloid regression in tissue is lacking.
Methods: All ATTRv amyloidosis patients on patisiran treatment at the University Medical Center of Groningen, the Netherlands, were evaluated for eligibility in a retrospective cohort study. Subcutaneous abdominal fat tissue aspirates were stained with Congo red as part of routine care. Congo red (CR) scores (0­­–4+) before and after patisiran initiation were extracted from the patient files and compared using the Wilcoxon signed-rank sum test. Patients without baseline or follow-up aspirates were excluded.
Results: Thirty-six of the 64 ATTRv amyloidosis patients on patisiran were included. Median serum transthyretin reduction was 82%. Prior to initiation of patisiran, CR-score increased in 50% and decreased in 19% of patients (p=.070). Within the first year of treatment with patisiran, CR-score increased in 18% and decreased in 27% of patients (p=.439). Between year one and two, CR-score increased in 8% and decreased in 69% of patients (p=.011). After two years of treatment, CR-score increased in 13% and decreased in 56% of patients compared to baseline (p=.029). See Figure 1.
Discussion: This is the first study to provide evidence of regression of amyloid in tissue of ATTRv amyloidosis patients treated with gene-silencing therapy, demonstrating a decrease in CR-scores after two years of treatment with patisiran.



**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Hendrea S.A. Tingen, department of Nuclear Medicine and Molecular Imaging, University Medical Centre Groningen, Groningen, The Netherlands

**Main Body of the Abstract**
**Introduction:** Patisiran, a small interfering RNA, improves neuropathy and cardiac parameters in hereditary ATTR (ATTRv) amyloidosis. Reductions in extracellular volume by cardiac magnetic resonance imaging and cardiac tracer uptake on bone scintigraphy in patients receiving patisiran suggest amyloid regression. However, evidence confirming amyloid regression in tissue is lacking.
**Methods:** All ATTRv amyloidosis patients on patisiran treatment at the University Medical Center of Groningen, the Netherlands, were evaluated for eligibility in a retrospective cohort study. Subcutaneous abdominal fat tissue aspirates were stained with Congo red as part of routine care. Congo red (CR) scores (0­­–4+) before and after patisiran initiation were extracted from the patient files and compared using the Wilcoxon signed-rank sum test. Patients without baseline or follow-up aspirates were excluded.
**Results**: Thirty-six of the 64 ATTRv amyloidosis patients on patisiran were included. Median serum transthyretin reduction was 82%. Prior to initiation of patisiran, CR-score increased in 50% and decreased in 19% of patients (p=.070). Within the first year of treatment with patisiran, CR-score increased in 18% and decreased in 27% of patients (p=.439). Between year one and two, CR-score increased in 8% and decreased in 69% of patients (p=.011). After two years of treatment, CR-score increased in 13% and decreased in 56% of patients compared to baseline (p=.029). See Figure 1.
**Discussion:** This is the first study to provide evidence of regression of amyloid in tissue of ATTRv amyloidosis patients treated with gene-silencing therapy, demonstrating a decrease in CR-scores after two years of treatment with patisiran.



Regression of amyloid load in subcutaneous fat tissue of hereditary transthyretin amyloidosis patients during treatment with patisiran PC140 (#465)

We invite you to attend the XIX International Symposium on Amyloidosis to be held in Rochester, MN.

This symposium is organized as a hybrid meeting (with the focus on in-person) held from Sunday, May 26 through Thursday, May 30, 2024.

Together with the ISA Board and members of Mayo Clinic, a very attractive scientific hybrid program is being planned. The program will cover a variety of types of systemic amyloidosis: ATTR (hereditary and wild-type), AL (light-chain), AA and less frequent forms. There will be key lectures, specific symposia including those company sponsored, oral presentations and poster sessions of accepted abstracts.

COURSE DESCRIPTION
This program will provide a comprehensive review of state-of-the-art education in systemic amyloidosis: basic science, pathophysiology, diagnosis, current and emerging treatments. Scientific presentations will include competitive oral and poster abstracts. The rapid evolution of scientific discovery and expanding treatment options has created tremendous interest in the field and this meeting will fill and important gap in educating scientists and clinicians.