Safety marginCriticised but acceptedBeyond the letter
Chronic rat and dog exposure margins below ICH M3(R2) expectations because exaggerated pharmacology limited dosing
Why: Dose-limiting exaggerated pharmacology; HCM patients would likely tolerate reduced cardiac contractility better than animals · Pharmacology or kinetics
“In both species, chronic RDT studies generally may not have explored the full range of aficamten mediated effects in naïve animals due to lack of exposure due to dose limiting aficamten-related (exaggerated) pharmacology. As a result, exposure margins in the chronic RDT studies in rat and dog are below what is expected in ICH M3(R2).”
✓ VerifiedEMA assessment report, p. 40Source ↗ “Hypercontractility is one of the pathological hallmarks of hypertrophic cardiomyopathy, and the indicated patient population would likely tolerate a reduction in cardiac contractility to a greater extent than animals or humans with 'normal' cardiac contractility.”
✓ VerifiedFDA integrated review, p. 111Source ↗ CarcinogenicityCriticised but acceptedBeyond the letter
High mortality in the 104-week rat carcinogenicity study forced early termination of dose groups
Why: Transgenic mouse data and totality of evidence indicate low carcinogenic potential · Weight of evidence
“The high mortality in the 104-week carcinogenicity necessitated early termination of dose groups.”
✓ VerifiedEMA assessment report, p. 40Source ↗ “The transgenic mouse data did not suggest carcinogenic risk and the available data does not suggest involvement of aficamten in pro-oncogenic pathways. Overall, the totality of evidence is sufficient to suggest that aficamten has a low carcinogenic potential.”
✓ VerifiedEMA assessment report, p. 40Source ↗ DARTQuestioned
Rabbit EFD study limited to maternally toxic exposures below the MRHD; considered insufficient
Why: Maternal toxicity limited exposures to below the MRHD
“When aficamten was administered orally in an embryo-foetal toxicity study in the rabbit, increases in the number of late resorptions were observed at maternally toxic exposures below the MRHD. As such this study is considered insufficient.”
✓ VerifiedEMA assessment report, p. 40Source ↗ Impurity or metaboliteAcceptedBeyond the letter
No dedicated carcinogenicity study for major metabolite M1a, covered at only 0.5-fold exposure in the 2-year rat study
Why: M1a non-genotoxic, no concerning signals in rodent studies; minimal carcinogenic risk by weight of evidence · Weight of evidence
“The 2-year rat study, which reached 0.5-fold exposure, similarly demonstrated no concerning signals. Furthermore, M1a was determined to be non-genotoxic based on a comprehensive battery of assays and weight-of-evidence evaluation. Collectively, these data indicate minimal carcinogenic risk for this metabolite, therefore, we conclude that a dedicated carcinogenicity study is not warranted.”
✓ VerifiedFDA integrated review, p. 110Source ↗