Updates on Emerging Therapies in Cardiac Light Chain (AL) Amyloidosis
Authors: Ehsan Hamid , Wahab Ahsan , Sana Muhammad Khawar , Faisal Muhammad Salman , Jaan Ali , Muneeb Ahmad , Sheikh Muhammad Mubashir , Anwer Faiz 
Published: November 2020

Introduction:
Amyloidosis is a disorder where misfolded proteins get deposited in different tissues. The most common of them is immunoglobulin light chain (AL) deposition, otherwise known as AL amyloidosis. Cardiac involvement generally correlates with poor prognosis, and treatment options are limited if presented late. Novel disease-modifying agents are being studied in on-going trials to optimize treatment strategy. This review aims to summarize the updates on upcoming treatment options for AL amyloidosis, particularly involving the heart.
Methodology:
We performed a comprehensive literature search on PubMed, clinicaltrials.gov, and Cochrane databases (last updated on May 20, 2020). We used MeSH terms along with their keywords and combined their results. The literature search generated a total of 652 references. Two independent reviewers screened the articles and shortlisted 21 clinical trials that were included in our final review.
Results:
Monoclonal antibodies (daratumumab, isatuximab, elotuzumab and birtamimab) are being studied as monotherapy and combinations in relapsed/refractory (RR) AL amyloidosis. Despite good data on efficacy and safety, Daratumumab has not been approved yet in this category for advanced cardiac amyloidosis patients. Isatuximab showed the overall hematological response (HR) of 56% in phase I trial in a combination regimen and is now being evaluated as monotherapy in phase II. In a recent phase III trial of RR AL amyloidosis patients, the median progression-free survival was assessed over 24.5 months. It was increased from 14.9 months (lenalidomide and dexamethasone alone) to 19.4 months (elotuzumab, lenalidomide, and dexamethasone).
Immunomodulators (lenalidomide, pomalidomide, thalidomide) are well studied for safety in other malignancies. Lenalidomide in various combinations has shown hematological response of greater than 60% in AL amyloidosis. Similarly, pomalidomide has shown an overall hematological response of 48-50% in two different early phase trials. Moreover, thalidomide was associated with significant toxicity in phase I/II trials and was discontinued.
Second-generation proteasome inhibitors (ixazomib and carfilzomib) were assessed in RR cases of AL amyloidosis. Ixazomib achieved a hematological response of 52%. However, carfilzomib has been associated with cardiovascular toxicity and a higher risk of hospitalization in phase I trials, making it unsuitable.
Venetoclax has shown encouraging results in multiple myeloma, particularly in t(11:14). 50% of AL amyloidosis cases have t(11:14) in whom venetoclax can be beneficial. A trial [NCT03000660] was suspended halfway citing clinical hold from regulatory authorities.
Alkylating agents, mainly bendamustine, are currently under study after it showed a survival advantage in heavily pretreated cases [NCT01222260].
Underexplored venues: Small interfering RNAs (siRNAs) have a favorable response and excellent toxicity profile in AL amyloidosis. Issues regarding half-life and delivery systems have limited their use. CAEL-101, a novel chimeric fibril-reactive monoclonal antibody (gG1κ 11-1F4), tolerated well with improved organ function in AL amyloidosis in an early phase trial where it improved global longitudinal strain from baseline -9.58 to -13.39. SB203580 + rapamycin combination works in synergy with the former inhibiting the p38 MAPK pathway markedly reducing the toxicity of light chain immunoglobulins on cardiac myocytes and the latter restoring the SB203580-induced autophagic dysregulation. Epigallocatechin-3-gallate (EGCG) was well tolerated and found non-inferior to standard chemotherapy in a small phase II trial [NCT01511263]. Serum amyloid P (SAP) is a chaperone protein in amyloid fibril formation. Anti-SAP antibodies have shown promising results with safe toxicity profile in phase I trial [NCT01777243] in non-cardiac involved patients. However, another trial in cardiac involved cases was terminated due to significant toxicity. Table 1
Conclusion:
Numerous drugs with novel mechanisms of actions are being studied, and results so far offer hope for improving the therapy & outcomes, especially in patients with cardiac involvement. The drug combination regimens lead to slow down the disease progression by interfering at multiple steps in the cascade of light chain synthesis, secretion, deposition, and organ clearance.

Disclosures
Anwer: Incyte, Seattle Genetics, Acetylon Pharmaceuticals, AbbVie Pharma, Astellas Pharma, Celegene, Millennium Pharmaceuticals.: Honoraria, Research Funding, Speakers Bureau.