Trikafta
elexacaftor, tezacaftor and ivacaftor
Species
RatDog
Longest study
39 wk
Genotox
Conducted Conducted
Carcinogenicity
Conducted Conducted
Repro
Conducted Conducted
First dose
Not conducted Not stated publicly
Speciesopen answer page →
Species
Rat and dog
“The rat was the pivotal rodent species in repeat dose toxicity studies with elexacaftor alone or in combination with tezacaftor or ivacaftor. The dog was the pivotal non-rodent species.”
Why that species
Not stated in public reviews
The reviews list the species but not why. For small molecules, ICH M3(R2) expects one rodent and one non-rodent species, chosen with in vitro metabolism, protein binding and exposure data compared with human.
“In vitro metabolic and plasma protein binding data for animals and humans and systemic exposure data (ICH S3A, Ref. 7) in the species used for repeated-dose toxicity studies generally should be evaluated before initiating human clinical trials.”
✓ VerifiedICH 2009: ICH M3(R2): Guidance on Nonclinical Safety Studies for the Conduct…, p. 11Source ↗
Surrogate molecule
No surrogate; the clinical compounds were tested
“In the 1-month triple combination study in dogs (VRT-1651445-TX-022), all animals survived until the end of dosing.”
Species: general tox
Rat and dog (up to 6 and 9 months), plus mouse; elexacaftor alone and with tezacaftor/ivacaftor
“general toxicity studies with either VX-445 alone or in combination with tezacaftor (VX-661) and ivacaftor (VX-770) were conducted in rats, mice, and dogs with dosing durations up to 6 months in rodents and 9 months in non-rodents.”
Species: DART
Rat and rabbit (separate studies of each component)
“separate reproductive and developmental studies were conducted with each active component of TRIKAFTA in pregnant rats and rabbits.”
Species: carcinogenicity
Elexacaftor: Tg.rasH2 mouse (6-month) and rat (2-year)
“A 6-month study in Tg.rasH2 transgenic mice showed no evidence of tumorigenicity at 50 mg/kg/day dose, the highest dose tested. A two-year study was conducted in rats to assess the carcinogenic potential of elexacaftor.”
Surrogate used in
No surrogate used; elexacaftor tested alone and in triple combination
“In the 1-month triple combination study in dogs (VRT-1651445-TX-022), all animals survived until the end of dosing.”
Study lengthopen answer page →
Longest pivotal study
39 (39-week dog, elexacaftor)
“When VX-445 was administered alone chronically (up to 39-week) in dogs (VX-445-TX-006), test item-related microscopic changes were noted at 14 mg/kg/day including hepatocellular hypertrophy, epithelium vacuolation in gallbladder, and testicular seminiferous tubule atrophy/degeneration.”
Pivotal GLP studies
Rat (up to 6 months) and dog (up to 9 months) studies of elexacaftor alone or with tezacaftor and ivacaftor
“As listed in the following table, general toxicity studies with either VX-445 alone or in combination with tezacaftor (VX-661) and ivacaftor (VX-770) were conducted in rats, mice, and dogs with dosing durations up to 6 months in rodents and 9 months in non-rodents.”
Route in tox
Oral (gavage)
“VX-445: A 26-week Oral (Gavage) Toxicity Study in Sprague Dawley Rats Followed by a 6-week Recovery Period”
Skipped studiesopen answer page →
Genotoxicity
Elexacaftor negative in bacterial and mammalian in vitro assays and an in vivo chromosomal damage assay
“Elexacaftor was not genotoxic in a bacterial and a mammalian in vitro assay in the presence or absence of S9 metabolizing mix. Elexacaftor was also not genotoxic in a chromosomal aberration assay in vivo.”
Carcinogenicity
Elexacaftor 6-month Tg.rasH2 mouse and 2-year rat: no tumorigenicity
“A 6-month study in Tg.rasH2 transgenic mice showed no evidence of tumorigenicity at 50 mg/kg/day dose, the highest dose tested. A two-year study was conducted in rats to assess the carcinogenic potential of elexacaftor. No evidence of tumorigenicity was observed in rats at elexacaftor oral doses up to 10 mg/kg/day”
Reproductive & developmental
Elexacaftor rat fertility: lower fertility, copulation and conception indices at high doses (NOAEL 55/25 mg/kg/day M/F)
“In conclusion, the NOAEL for reproductive toxicity was determined to be 55 mg/kg/day in males and 25 mg/kg/day in females based on lower male and female fertility, male copulation, and female conception indices at 75 mg/kg/day (males) and 35 mg/kg/day (females).”
Safety pharmacology
Elexacaftor: no changes in temperature, blood pressure, heart rate or ECG in telemetered dogs (single dose up to 30 mg/kg nominal, 24.78 mg/kg measured)
“Effects of elexacaftor on the cardiovascular system were assessed in telemetered dogs. A single dose of elexacaftor up to a nominal dose of 30 mg/kg (24.78 mg/kg actually measured) did not result in any changes in body temperature, blood pressure, pulse pressure, heart rate, or ECGs.”
Genotox: Ames
Elexacaftor: negative
“Elexacaftor was negative for genotoxicity in the following assays: Ames test for bacterial gene variant, in vitro mammalian cell micronucleus assay in TK6 cells, and in vivo mouse micronucleus test.”
Genotox: in vitro mammalian
Elexacaftor in vitro micronucleus (TK6 cells): negative
“Elexacaftor was negative for genotoxicity in the following assays: Ames test for bacterial gene variant, in vitro mammalian cell micronucleus assay in TK6 cells, and in vivo mouse micronucleus test.”
Genotox: in vivo
Elexacaftor mouse micronucleus: negative
“Elexacaftor was negative for genotoxicity in the following assays: Ames test for bacterial gene variant, in vitro mammalian cell micronucleus assay in TK6 cells, and in vivo mouse micronucleus test.”
Carcinogenicity model
Elexacaftor: 6-month Tg.rasH2 mouse (negative at 50 mg/kg/day); 2-year rat
“A 6-month study in Tg.rasH2 transgenic mice showed no evidence of tumorigenicity at 50 mg/kg/day dose, the highest dose tested. A two-year study was conducted in rats to assess the carcinogenic potential of elexacaftor.”
Carcinogenicity timing
Elexacaftor 6-month rasH2 mouse completed; 2-year rat to be completed after approval (postmarketing requirement)
“negative in teratogenicity and carcinogenicity assays (based on the 6-month study in mouse only; the 2-year carcinogenicity study in rat will be completed as a post-marketing requirement)”
hERG / QT
Elexacaftor: 31.2% hERG inhibition at 30 µM; low QT risk at clinical concentrations
“VX-445 inhibited potassium hERG channel by only 31.2 ± 2.4% at 30 μM, suggesting a low risk for QT prolongation at clinical relevant plasma concentrations.”
First doseopen answer page →
First-in-human starting dose
Not stated in public reviews
Why it's blank
The public FDA and EMA reviews of Trikafta don't say how the first human dose was chosen. That rationale is in the IND, which is confidential, so it is missing for most approved products.
How it's usually set for small molecules outside oncology
Find the highest dose with no adverse effects (NOAEL) in each animal species, convert it to a human equivalent dose, usually by body surface area, pick the most appropriate species, then divide by a safety factor (default 10) to get the maximum recommended starting dose.
“In general, one should consider using a safety factor of at least 10. The MRSD should be obtained by dividing the HED by the safety factor.”
This product's starting point
NOAEL / key findings: Deaths with gastric glandular mucosal erosion at high doses; NOAEL 15 mg/kg/day (4-12x human AUC) (FDA multi-discipline review, p. 44)
NOAEL / key findings
Deaths with gastric glandular mucosal erosion at high doses; NOAEL 15 mg/kg/day (4-12x human AUC)
“Multiple deaths/euthanasia were noted in those animals with the findings of decreased food intake leading to lower body weight and declining clinical condition with erosion of the glandular mucosa of the stomach. There was no adverse changes identified at 15 mg/kg/day; this dose level was considered as the NOAEL corresponding to AUC values 4 (males) or 12 (females) times the recommended human dose.”
Risksopen answer page →
Immune & cytokine safety
Lymphoid depletion in the thymus
“Microscopic correlates consisted of cortical hypertrophy/vacuolation in the adrenal glands, atrophy in the prostate, secretory depletion in the seminal vesicles/coagulating glands, germ cell debris/oligospermia in the epididymides, and lymphoid depletion in the thymus.”
Biodistribution & persistence
Elexacaftor crosses blood-brain barrier (brain ~3-fold below plasma); no preferential melanin binding
“VX-445-related radioactivity crossed the blood-brain barrier, but measured concentrations in the brain were about 3-fold lower relative to plasma. A tissue distribution study in Long-Evans rats showed no significant distribution to melanin-containing tissues (skin, eyes), indicating that VX-445 did not preferentially associate with melanin.”
Modality-specific risk
Major active human metabolite M23 with low nonclinical exposure margins (MIST)
“Levels of M23 formed in nonclinical species were generally lower than in humans, resulting in relatively low exposure margins in some cases.”
Anti-drug antibodies: animals
Not stated in public reviews
Not reported in the public reviews. Reviewers summarise selectively, so this usually means it wasn't discussed publicly, not that it wasn't studied.
Anti-drug antibodies: patients
Not stated in public reviews
Not reported in the public reviews. Reviewers summarise selectively, so this usually means it wasn't discussed publicly, not that it wasn't studied.
Label warnings
Boxed warning: Drug-induced liver injury and liver failure
- Drug-Induced Liver Injury and Liver Failure
- Hypersensitivity Reactions, Including Anaphylaxis
- Intracranial Hypertension
- Neuropsychiatric Events, Including Suicidal Thoughts and Behaviors
- Concomitant Use with CYP3A Inducers
- Concomitant Use with CYP3A Inhibitors
- Cataracts
HepatotoxicityHypersensitivity & infusion reactionsCardiovascularPsychiatricOcular toxicity
US prescribing information, Boxed Warning and Warnings and PrecautionsDailyMed ↗
Tox packageopen answer page →
Before first-in-human
First-in-human: where
Not stated in public reviews
Not reported in the public reviews. Reviewers summarise selectively, so this usually means it wasn't discussed publicly, not that it wasn't studied.
Repeat-dose tox before first-in-human
Not stated in public reviews
Not reported in the public reviews. Reviewers summarise selectively, so this usually means it wasn't discussed publicly, not that it wasn't studied.
First-in-human starting dose
Not stated in public reviews
Why it's blank
The public FDA and EMA reviews of Trikafta don't say how the first human dose was chosen. That rationale is in the IND, which is confidential, so it is missing for most approved products.
How it's usually set for small molecules outside oncology
Find the highest dose with no adverse effects (NOAEL) in each animal species, convert it to a human equivalent dose, usually by body surface area, pick the most appropriate species, then divide by a safety factor (default 10) to get the maximum recommended starting dose.
“In general, one should consider using a safety factor of at least 10. The MRSD should be obtained by dividing the HED by the safety factor.”
This product's starting point
NOAEL / key findings: Deaths with gastric glandular mucosal erosion at high doses; NOAEL 15 mg/kg/day (4-12x human AUC) (FDA multi-discipline review, p. 44)
Longest repeat-dose systemic studies
Longest repeat-dose study and recovery
39-week dog (elexacaftor, oral) with 6-week recovery
“VX-445: A 39-week Oral (Gavage) Toxicity and Toxicokinetic Study in Beagle Dogs With a 26-week Interim Sacrifice and 6-week Recovery Period”
Pivotal GLP studies
Rat (up to 6 months) and dog (up to 9 months) studies of elexacaftor alone or with tezacaftor and ivacaftor
“As listed in the following table, general toxicity studies with either VX-445 alone or in combination with tezacaftor (VX-661) and ivacaftor (VX-770) were conducted in rats, mice, and dogs with dosing durations up to 6 months in rodents and 9 months in non-rodents.”
DART package
Species: DART
Rat and rabbit (separate studies of each component)
“separate reproductive and developmental studies were conducted with each active component of TRIKAFTA in pregnant rats and rabbits.”
Reproductive & developmental
Elexacaftor rat fertility: lower fertility, copulation and conception indices at high doses (NOAEL 55/25 mg/kg/day M/F)
“In conclusion, the NOAEL for reproductive toxicity was determined to be 55 mg/kg/day in males and 25 mg/kg/day in females based on lower male and female fertility, male copulation, and female conception indices at 75 mg/kg/day (males) and 35 mg/kg/day (females).”
PPND / ePPND: when
PPND in rat (elexacaftor) completed before the marketing application
“A peri- and postnatal development study with elexacaftor was conducted in rats.”
Carcinogenicity
Species: carcinogenicity
Elexacaftor: Tg.rasH2 mouse (6-month) and rat (2-year)
“A 6-month study in Tg.rasH2 transgenic mice showed no evidence of tumorigenicity at 50 mg/kg/day dose, the highest dose tested. A two-year study was conducted in rats to assess the carcinogenic potential of elexacaftor.”
Carcinogenicity model
Elexacaftor: 6-month Tg.rasH2 mouse (negative at 50 mg/kg/day); 2-year rat
“A 6-month study in Tg.rasH2 transgenic mice showed no evidence of tumorigenicity at 50 mg/kg/day dose, the highest dose tested. A two-year study was conducted in rats to assess the carcinogenic potential of elexacaftor.”
Carcinogenicity timing
Elexacaftor 6-month rasH2 mouse completed; 2-year rat to be completed after approval (postmarketing requirement)
“negative in teratogenicity and carcinogenicity assays (based on the 6-month study in mouse only; the 2-year carcinogenicity study in rat will be completed as a post-marketing requirement)”
Safety marginopen answer page →
Safety margin at NOAEL
Elexacaftor 26-week rat NOAEL 15 mg/kg/day: 4x (males) to 12x (females) human AUC
“There was no adverse changes identified at 15 mg/kg/day; this dose level was considered as the NOAEL corresponding to AUC values 4 (males) or 12 (females) times the recommended human dose.”
NOAEL / key findings
Deaths with gastric glandular mucosal erosion at high doses; NOAEL 15 mg/kg/day (4-12x human AUC)
“Multiple deaths/euthanasia were noted in those animals with the findings of decreased food intake leading to lower body weight and declining clinical condition with erosion of the glandular mucosa of the stomach. There was no adverse changes identified at 15 mg/kg/day; this dose level was considered as the NOAEL corresponding to AUC values 4 (males) or 12 (females) times the recommended human dose.”
Efficacy evidenceopen answer page →
Efficacy evidence
CF patient-derived human bronchial epithelial (HBE) cells; increased CFTR processing and chloride transport
“Alone and in combination with tezacaftor and ivacaftor, elexacaftor facilitates processing and trafficking of CFTR leading to increased chloride transport in HBE cells collected from CF patients.”
Why that model
No validated animal model of CF; drugs act specifically on mutant human CFTR
“There is no validated animal model for CF that fully mimics the human multi organ affected disease. Furthermore, the proposed treatment is specific for mutated CFTR proteins.”
Reviewer's view of the efficacy data
EMA: in vitro-only pharmacology acceptable given no validated CF animal model
“As there is no validated animal model for CF that fully mimics the human multi organ affected disease and all three components bind specifically to CFTR, the use of in vitro systems to study the pharmacology of elexacaftor only or in combination with tezacaftor and ivacaftor can be accepted.”
Flexibilityopen answer page →
Flexibility accepted
CarcinogenicityAccepted with a conditionBeyond the letter
2-year rat carcinogenicity study of elexacaftor ongoing at approval; completed as a postmarketing requirement
Why: Unmet medical need in the proposed indication · Rare disease / unmet need
“A 2-year carcinogenicity study in rats (Study VX-445-TX-015) is ongoing and the division agreed that this study could be completed as a Post-Marketing Requirement based on the unmet medical need in the proposed indication (communication dated Jun 28, 2018).”
“The nonclinical team recommends approval with a 2-year carcinogenicity study in rats as a post-marketing requirement.”
DARTAcceptedBeyond the letter
Potential synergistic effects of the triple combination on fertility not investigated
Why: Rat fertility findings occur at exposures above clinical exposure · Pharmacology or kinetics
“However, potential synergistic effects on fertility were not investigated with the triple combination which is acceptable by CHMP since the observation in rat occurs at exposures above those reached in clinic.”
Safety marginVerdict not stated
No NOAEL for males in the rat triple-combination study: adverse body weight effects at the lowest dose
“However, the adverse body weight effects in males already at the lowest dose result in a NOAEL that cannot be determined for male animals.”
Efficacy modelAcceptedBeyond the letter
No in vivo efficacy model; pharmacology studied only in vitro (CF patient bronchial epithelial cells)
Why: No validated animal model of CF; all three components bind specifically to CFTR · Other reason
“As there is no validated animal model for CF that fully mimics the human multi organ affected disease and all three components bind specifically to CFTR, the use of in vitro systems to study the pharmacology of elexacaftor only or in combination with tezacaftor and ivacaftor can be accepted.”
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