Tafamidis polyneuropathy amelioration requires modest increases in transthyretin stability even though increases in plasma native TTR and decreases in non-native TTR do not predict response.

Cecília Monteiro, Jaleh S Mesgarzadeh, João Anselmo, Joana Fernandes, Marta Novais, Carla Rodrigues, David L Powers, Evan T Powers, Teresa Coelho, Jeffery W Kelly

Amyloid : the international journal of experimental and clinical investigation : the official journal of the International Society of Amyloidosis 2023 Mar

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TTR aggregation causes hereditary transthyretin (TTR) polyneuropathy (ATTRv-PN) in individuals with destabilised TTR variants. ATTRv-PN can be treated with ligands that bind TTR and prevent aggregation. One such ligand, tafamidis, is widely approved to treat ATTRv-PN. We explore how TTR stabilisation markers relate to clinical efficacy in 210 ATTRv-PN patients taking tafamidis. TTR concentration in patient plasma was measured before and after tafamidis treatment using assays for native or combined native + non-native TTR. TTR tetramer dissociation kinetics, which are slowed by tafamidis binding, were also measured. Native TTR levels increased by 56.8% while combined native + non-native TTR levels increased by 3.1% after 24 months of tafamidis treatment, implying that non-native TTR decreased. Accordingly, the fraction of native TTR increased from 0.54 to 0.71 with tafamidis administration. Changes in native and non-native TTR levels were uncorrelated with clinical response to tafamidis. TTR tetramer dissociation generally slowed to an extent consistent with ∼40% of TTR being tafamidis-bound. Male non-responders had a lower extent of binding. Native and non-native TTR concentration changes cannot be used as surrogate measures for therapeutic efficacy. Also, successful tafamidis therapy requires only moderate TTR stabilisation. Male patients may benefit from higher tafamidis doses.

Citation

Cecília Monteiro, Jaleh S Mesgarzadeh, João Anselmo, Joana Fernandes, Marta Novais, Carla Rodrigues, David L Powers, Evan T Powers, Teresa Coelho, Jeffery W Kelly. Tafamidis polyneuropathy amelioration requires modest increases in transthyretin stability even though increases in plasma native TTR and decreases in non-native TTR do not predict response. Amyloid : the international journal of experimental and clinical investigation : the official journal of the International Society of Amyloidosis. 2023 Mar;30(1):81-95