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RecruitingNCT07283770Updated Oct 19, 2026

Evaluation of VX-581 in Healthy Participants and in Participants With Cystic Fibrosis

A Phase 1 interventional study of VX-581 and Placebo in Cystic Fibrosis, sponsored by Vertex Pharmaceuticals Incorporated. Recruiting at 1 site in United States. Open to participants aged 18 Years to 55 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-10-19.

Sponsored by Vertex Pharmaceuticals Incorporated · Phase 1, Interventional, and Treatment

From the registry’s dates

  • Started Dec 2025; still recruiting 11 months later.
Updated Oct 19, 2026Primary completion movedStudy completion moved+5 moreGo to Updates ↓
Phase
Phase 1
Study type
Interventional
Enrollment
152
Allocation
Randomized
Ages
18 Years to 55 Years
Sex
All
01

Study summary

The purpose of this study is to evaluate the safety, tolerability, and pharmacokinetics of single dose of VX-581 and multiple ascending doses of VX-581 alone and in combination with tezacaftor (TEZ)/deutivacaftor (D-IVA) or D-IVA in healthy participants. The study will also evaluate the safety, tolerability, and pharmacokinetics of VX-581 administered in combination with D-IVA with or without TEZ in participants with cystic fibrosis (CF).

Read the detailed description

The study is being conducted to evaluate the safety, tolerability, and pharmacokinetics of single and multiple ascending doses of VX-581 in healthy participants and in participants with CF. VX-581 will be administered alone and in combination with TEZ and D-IVA. The study consists of Screening Phase, Run-In Phase (CF only), Treatment Phase and Safety Follow-up Phase.

Note: This clinical trial information was submitted voluntarily under the applicable law and, therefore, certain submission deadlines may not apply. (That is, clinical trial information for this applicable clinical trial was submitted under section 402(j)(4)(A) of the Public Health Service Act and 42 CFR 11.60 and is not subject to the deadlines established by sections 402(j)(2) and (3) of the Public Health Service Act or 42 CFR 11.24 and 11.44.).

02

Conditions studied

  • Cystic Fibrosis

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03

In context

Cystic Fibrosis

1,619 studies on the registry are indexed under Cystic Fibrosis; 199 are open to participants now.

This study's planned enrollment of 152 is above the median of 36 across 1,051 interventional studies indexed under Cystic Fibrosis.

Browse Cystic Fibrosis studies →

Lead sponsor

Vertex Pharmaceuticals Incorporated is the lead sponsor of 249 studies on the registry; 17 are open to participants now.

Of its 106 completed or terminated interventional studies of FDA-regulated products, 53 (50%) have results posted.

Browse Vertex Pharmaceuticals Incorporated studies →

Counted across the registry records on this site, refreshed daily.

04

Who can participate

The criteria were revised on the registry on Oct 19, 2026. See what changed

Ages eligible
18 Years to 55 Years
Sexes eligible
All
Accepts healthy volunteers
Yes

Eligibility criteria

Key Inclusion Criteria:

  • Parts A, B, C:

    • (BMI) of 18.0 to 32.0 kilogram per meter square (kg/m\^2)
    • A total body weight of more than (>) 50 kg

  • Part D:

    • Confirmed diagnosis of CF

Key Exclusion Criteria:

  • Parts A, B, C:

    • History of febrile illness or other acute illness that has not fully resolved within 14 days before the first dose of study drug
    • Any condition possibly affecting drug absorption

  • Part D:

    • History of cirrhosis with or without portal hypertension.

Other protocol defined Inclusion/Exclusion criteria may apply.

Terms in these criteria, in plain language(2)

Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.

BMI (body mass index)

Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.

What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.

Clinically significant

Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.

05

Study design

Phase
Phase 1
Primary purpose
Treatment
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Quadruple (Participant, Care provider, Investigator, Outcomes assessor)
Enrollment
152 participants (estimated)

Study arms

  • Experimental
    Part A: Single Ascending Dose

    Participants will be randomized to receive a single dose of VX-581.

    Drug: VX-581

  • Placebo comparator
    Placebo: Part A

    Participants will be randomized to receive a single dose of placebo matched to VX-581.

    Drug: Placebo

  • Experimental
    Part B: Multiple Ascending Dose

    Participants will be randomized to receive multiple doses of VX-581.

    Drug: VX-581

  • Placebo comparator
    Placebo: Part B

    Participants will be randomized to receive multiple doses of placebo matched to VX-581.

    Drug: Placebo

  • Experimental
    Part C: VX-581 with TEZ/D-IVA or D-IVA

    Participants will be randomized to receive multiple doses VX-581 in combination with TEZ/D-IVA or D-IVA.

    Drug: VX-581 · Drug: D-IVA · Drug: TEZ

  • Placebo comparator
    Placebo: Part C

    Participants will be randomized to receive placebo matched to VX-581 in combination with TEZ/D-IVA or D-IVA.

    Drug: Placebo · Drug: D-IVA · Drug: TEZ

  • Experimental
    Part D: VX-581 with TEZ/D-IVA or D-IVA in CF

    Participants with CF will enter a run-in period and receive ELX/TEZ/IVA. Following the run-in period participants will receive VX-581 in combination with TEZ/D-IVA or D-IVA in the treatment period. Following the treatment period, participants will enter a 14-day Washout Period and receive ELX/TEZ/IVA. (Part D will be open-label)

    Drug: D-IVA · Drug: TEZ · Drug: ELX/TEZ/IVA · Drug: VX-581 · Drug: IVA

Interventions

  • DrugVX-581

    Suspension for Oral Administration.

  • DrugPlacebo

    Suspension for Oral Administration.

  • DrugD-IVA

    Tablet for Oral Administration.

    Also known as: deutivacaftor, VX-561

  • DrugTEZ

    Tablet for Oral Administration.

    Also known as: tezacaftor, VX-661

  • DrugELX/TEZ/IVA

    Drug pages: Elexacaftor · Tezacaftor · Ivacaftor

    Fixed dose combination (FDC) Tablets for Oral Administration.

    Also known as: VX-445/VX-661/VX-770, elexacaftor/tezacaftor/ivacaftor

  • DrugVX-581

    Tablets for Oral Administration.

  • DrugIVA

    Tablet for Oral Administration.

    Also known as: VX-770, Ivacaftor

06

What researchers measure

Primary outcomes

  1. Part A: Safety and Tolerability as Assessed by Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)

    Time frame: From Day -1 up to Day 8

  2. Part B: Safety and Tolerability as Assessed by Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)

    Time frame: From Day -1 up to Day 17

  3. Part C: Safety and Tolerability as Assessed by Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)

    Time frame: From Day -1 up to Day 17

  4. Part D: Safety and Tolerability as Assessed by Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)

    Time frame: From Signing of Informed Consent up to Day 105

Secondary outcomes

  1. Part A: Maximum Observed Plasma Concentration (Cmax) of VX-581

    Time frame: On Day 1

  2. Part A: Area Under the Concentration Versus Time Curve From the Time of Dosing Up to 24 Hours (AUC0-24h) Post-Dose of VX-581

    Time frame: On Day 1

  3. Part B: Cmax of VX-581

    Time frame: On Days 1, 7, and 10

  4. Part B: AUC0-24h Post-Dose of VX-581

    Time frame: On Days 1, 7, and 10

  5. Part C: Cmax of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)

    Time frame: On Days 1, 7, and 10

  6. Part C: AUC0-24h Post Dose of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)

    Time frame: On Days 1, 7, and 10

  7. Part D: Cmax of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)

    Time frame: On Day 1 and Day 28

  8. Part D: AUC0-24h Post Dose of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)

    Time frame: On Day 1 and Day 28

  9. Part D: Absolute Change in Sweat Chloride (SwCl)

    Time frame: From Baseline Up To Day 28

07

Study locations

1 of 1 sites recruiting
  • Altasciences - Kansas City
    Overland Park, Kansas 66212, United States
    Recruiting
08

References and documents

Individual participant data

Plan to share: No — Details on Vertex data sharing criteria and process for requesting access can be found at: https://www.vrtx.com/our-science/clinical-trials-data-sharing/

No publications or documents are linked to this record.

09

Timeline

1 registry update since Sep 25, 2026
ElapsedEstimatedEstimated, not yet reachedDate before it movedWhere the date was before it movedSimilar studies: half by the dot; the band is the middle halfHalf of similar studies reached it by the dot; the band is the middle half, from a quarter to three quarters

Started Dec 2025 (actual). Primary completion is estimated for Jul 2027, 19 months after the start.

Of 39 industry-sponsored phase 1 interventional studies under Cystic Fibrosis, half reached primary completion within 8 months of starting (the median), counting those still running; a quarter within 2 and three quarters within 16. This study's planned 19 months is above that.

Counting every sponsor, half of 62 studies reached it within 10 months; a quarter within 5 and three quarters within 34.

Since we started tracking on Sep 25, 2026, the dates moved once, on Oct 19, 2026: primary completion Nov 2026 → Jul 2027 and completion Nov 2026 → Jul 2027.

Earlier changes are on the record history on ClinicalTrials.gov ↗

How these figures are worked out, and which studies are left out of them.

Registered
Dec 4, 2025
First posted
Dec 16, 2025
StartActual
Dec 9, 2025
Primary completionEst.
Jul 12, 2027was Nov 2026
CompletionEst.
Jul 12, 2027was Nov 2026
Last update
Oct 19, 2026
What these dates mean
Start.
When the first participant enrolled; while estimated, when the study expects to open to recruitment.
Primary completion.
When the last participant was examined or treated to collect data for the study's main question, its primary outcome. A study that stopped early gives the date its data collection stopped.
Completion.
When the last participant's last visit took place, for every outcome, secondary ones and side effects included: the end of the study. Often later than primary completion, sometimes the same day.
Actual and Est.
Actual means the registry says the date has happened. Est. (estimated) is a date the sponsor plans or expects. It can still move, and the sponsor is expected to change it to actual once it has passed.
Primary completion
Nov 19, 2026→Jul 12, 2027
Oct 19, 2026
Study completion
Nov 19, 2026→Jul 12, 2027
Oct 19, 2026
Enrollment
136→152
Oct 19, 2026
Eligibility
6 criteria added
What changed in the criteria
  • AddedParts A, B, C:
  • AddedPart D:
  • AddedConfirmed diagnosis of CF
  • AddedParts A, B, C:
  • AddedPart D:
  • AddedHistory of clinically significant cirrhosis with or without portal hypertension.
Oct 19, 2026
Interventions
Added Drug: ELX/TEZ/IVA·Drug: VX-581·Drug: IVA. Arms added: Part D: VX-581 with TEZ/D-IVA or D-IVA in CF
Oct 19, 2026
Primary outcomes
1 added
What changed in the outcomes
  • AddedPart D: Safety and Tolerability as Assessed by Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)Time frame: From Signing of Informed Consent up to Day 105
Oct 19, 2026
Secondary outcomes
4 edited, 3 added
What changed in the outcomes
  • EditedPart B: Maximum Observed Plasma Concentration (Cmax) of VX-581Time frame: On Days 1, 7, and 10
  • EditedPart B: Area Under the Concentration Versus Time Curve From the Time of Dosing Up to 24 Hours (AUC0-24h) Post-Dose of VX-581Time frame: On Days 1, 7, and 10
  • EditedPart C: Maximum Observed Plasma Concentration (Cmax) of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)Time frame: On Days 1, 7, and 10
  • EditedPart C: Area Under the Concentration Versus Time Curve From the Time of Dosing Up to 24 Hours (AUC0-24h) Post Dose of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)Time frame: On Days 1, 7, and 10
  • AddedPart D: Cmax of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)Time frame: On Day 1 and Day 28
  • AddedPart D: AUC0-24h Post Dose of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)Time frame: On Day 1 and Day 28
  • AddedPart D: Absolute Change in Sweat Chloride (SwCl)Time frame: From Baseline Up To Day 28
Oct 19, 2026
Title
Dose Escalation Study Evaluating the Safety and Pharmacokinetics of VX-581 in Healthy Participants→Evaluation of VX-581 in Healthy Participants and in Participants With Cystic Fibrosis
Oct 19, 2026
Show all 1 update
  1. Oct 19, 2026
    Primary completion Nov 19, 2026→Jul 12, 2027
    Study completion Nov 19, 2026→Jul 12, 2027
    Enrollment 136→152
    Eligibility 6 criteria added
    What changed in the criteria
    • AddedParts A, B, C:
    • AddedPart D:
    • AddedConfirmed diagnosis of CF
    • AddedParts A, B, C:
    • AddedPart D:
    • AddedHistory of clinically significant cirrhosis with or without portal hypertension.
    Primary outcomes 1 added
    What changed in the outcomes
    • AddedPart D: Safety and Tolerability as Assessed by Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)Time frame: From Signing of Informed Consent up to Day 105
    Secondary outcomes 4 edited, 3 added
    What changed in the outcomes
    • EditedPart B: Maximum Observed Plasma Concentration (Cmax) of VX-581Time frame: On Days 1, 7, and 10
    • EditedPart B: Area Under the Concentration Versus Time Curve From the Time of Dosing Up to 24 Hours (AUC0-24h) Post-Dose of VX-581Time frame: On Days 1, 7, and 10
    • EditedPart C: Maximum Observed Plasma Concentration (Cmax) of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)Time frame: On Days 1, 7, and 10
    • EditedPart C: Area Under the Concentration Versus Time Curve From the Time of Dosing Up to 24 Hours (AUC0-24h) Post Dose of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)Time frame: On Days 1, 7, and 10
    • AddedPart D: Cmax of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)Time frame: On Day 1 and Day 28
    • AddedPart D: AUC0-24h Post Dose of VX-581, TEZ (if administered), D-IVA and their Metabolite(s)Time frame: On Day 1 and Day 28
    • AddedPart D: Absolute Change in Sweat Chloride (SwCl)Time frame: From Baseline Up To Day 28
    Interventions Added Drug: ELX/TEZ/IVA·Drug: VX-581·Drug: IVA. Arms added: Part D: VX-581 with TEZ/D-IVA or D-IVA in CF
    Title Dose Escalation Study Evaluating the Safety and Pharmacokinetics of VX-581 in Healthy Participants→Evaluation of VX-581 in Healthy Participants and in Participants With Cystic Fibrosis
    + 3 other changes: index terms, verification date and description

From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗

10

Registry details

Key details

Study ID
NCT07283770
Lead sponsor
Vertex Pharmaceuticals Incorporated
Responsible party
Sponsor
First posted
Dec 16, 2025
Start date
Dec 9, 2025
Primary completion
Jul 12, 2027 (estimated)
Completion
Jul 12, 2027 (estimated)
Last update
Oct 19, 2026

Study contacts

Medical Information
Contact
medicalinfo@vrtx.com
617-341-6777

Oversight

FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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