SKY-0515

Budget impact modelIn development

Overview

Estimated change in the drug and monitoring spending of a United States health plan over 3 years when SKY-0515, an investigational once-daily oral huntingtin-lowering drug, is added to standard of care for adult members with Huntington's disease who meet the functional criterion of its pivotal trials.

Perspective

A United States health plan paying drug acquisition and monitoring costs for its members. Member cost sharing and patient assistance are excluded. No manufacturer rebate is applied beyond the 15% payer discount contained in the placeholder price.

Time horizon

3 years, undiscounted

Price basis

SKY-0515 is not approved in any country and no manufacturer price had been published on 1 October 2026. The drug cost is a placeholder: the annual cost that a published United States cost-effectiveness analysis assumed for tominersen, an intrathecal huntingtin-lowering therapy, which is three injections per year at $106,250 each, a price taken from a spinal muscular atrophy treatment after a 15% payer discount, in 2024 dollars. Monitoring is costed at 2026 Medicare fee schedule national amounts.

Inputs checked

2026-10-01

Every field can be changed, and the results recalculate as it is. A field is marked with the basis of its value, which links to the quote, data row, or assumption behind it. PMPM is the cost per member per month.

Target population

Market share

Share of eligible patients on each treatment during each year. Standard of care alone takes whatever share the other rows leave. Assumption

Treatment costs

Monitoring

Cost per patient per year on treatment

Results

Budget impact by year

Budget impact by cost category

Patients on treatment and treatment cost, by treatment

Sensitivity analysis

One-way sensitivity analysis of the 3-year budget impact

Each input is set to its low and its high value in turn, with every other value as entered above. The 6 inputs that move the result most are shown; the vertical line marks the current result, +$7,600,136.

Scenario analyses

Inputs and sources

A value on a quoted source carries the quote as the evidence report holds it, linked to the document it came from. A value on published data names the row of the file it was read from. An assumption is a value no source states.

• Plan members

  1,000,000Assumption

  A plan of 1,000,000 members is the base case of the model. A plan enters its own enrollment.

• Prevalence of diagnosed Huntington's disease

  9.40 per 100,000Range 6.52 per 100,000 to 13.70 per 100,000Quoted source

  The base case is the 2024 annual prevalence in a United States all-state closed claims database of 38.4 million continuously enrolled people. That study was designed to test an analysis platform. It carries a confirmed case forward into later years, so the 2024 value counts every case identified from 2020 to 2024, and it reports neither the payer mix nor whether people who died were removed from later years. The low bound is the age-adjusted rate in commercial claims from 2003 to 2016 (6.52), and the high bound is the multisource estimate for British Columbia (13.7). The bounds describe a plan with members of every payer type; a plan of one payer type is a scenario. As a cross-check, weighting the rates of 6.52 (commercial), 13.1 (Medicare, aged 65 years or older), and 15.2 (Medicaid, younger than 65 years) by a member mix of 61.0%, 16.4%, and 22.6% gives 9.6 per 100,000. At the base case a plan of 1,000,000 members has 94 members with diagnosed Huntington's disease.

  • “9.4 (8.9-9.8)”

    SourceFrisch et al. (2026)

  • “Of the 59 million individuals in the study population, 38.4 million (65.1%) met the continuous enrollment requirement of 12 months during the study period.”

    SourceFrisch et al. (2026)

  • “We estimated a cumulative age-adjusted HD frequency rate of 6.52 per 100,000 persons”

    SourceBruzelius et al. (2019)

  • “Using an insurance database of over 67 million enrollees, we retrospectively identified a cohort of 3,707 individuals diagnosed with Huntington’s disease between 2003–2016.”

    SourceBruzelius et al. (2019)

  • “Prevalence of HD was estimated at 13.7 per 100,000 (95% confidence interval [CI]: 12.6-14.8 per 100,000) in the general population, and 17.2 per 100,000 (95% CI: 15.8-18.6 per 100,000) in the Caucasian population.”

    SourceFisher and Hayden (2014)

  • “In the Medicare population, 1,941 prevalent and 819 incident cases of HD were identified in 2017, corresponding to a prevalence proportion of 13.1 per 100,000 persons and incidence rate of 6.1 per 100,000 person-years. In the Medicaid population, 353 prevalent cases of HD were identified in 2014, corresponding to a prevalence proportion of 15.2 per 100,000 persons.”

    SourceExuzides et al. (2022b)

  • Health Insurance Coverage of the Total Population, 2024, United States: Employer 0.48634, Non-Group 0.06562, Medicaid 0.20445, Medicare 0.14832. Commercial (employer plus non-group), Medicare, and Medicaid are 61.0%, 16.4%, and 22.6% of the members in those three groups.

    SourceKFF (2024)

• Share aged 25 years or older

  98.8%Quoted source

  The pivotal trials enroll people aged 25 years or older. In commercial claims 1.18% of diagnosed people were aged 20 years or younger, so 100% less 1.18% is 98.8%. The share aged 21 to 24 years is not reported and stays in the population.

  • “Among those diagnosed, 1.18% (n = 44) were identified as 20 years old or less, indicating juvenile onset.”

    SourceBruzelius et al. (2019)

• Share genetically confirmed with 40 or more CAG repeats

  100%Assumption

  The pivotal trials require genetic confirmation with 40 or more CAG repeats. No source reports the share of diagnosed patients with a test result on record or with 36 to 39 repeats, so the base case applies no reduction. A plan with its own figure enters it here.

  • “Huntington's Disease confirmed through genetic testing, with a specific change in exon 1 of the HTT gene (CAG repeat of 40 or more).”

    SourceClinicalTrials.gov NCT07378644

  • “The diagnosis of HD is established in a proband with suggestive findings and a heterozygous CAG trinucleotide repeat expansion in HTT identified by molecular genetic testing (see Table 1).”

    SourceCaldeira Brás et al. (2026)

• Share with a Total Functional Capacity score of 10 or more

  43%Range 32.7% to 74%Assumption

  The pivotal trials require a Total Functional Capacity score of 10 or more. No source reports the share of diagnosed patients with a score of 10 or more, so the value is an assumption derived from a stage distribution. Of 2,584 North American Enroll-HD participants with manifest disease at their baseline visit (845 + 1,068 + 540 + 116 + 15), 845 (32.7%) were in stage I (score 11 to 13) and 1,068 (41.3%) were in stage II (score 7 to 10). The base case adds one quarter of stage II to stage I, assuming the four scores from 7 to 10 are equally frequent: 32.7% + 41.3% / 4 = 43.0%. The low bound is stage I alone (32.7%) and the high bound is stages I and II together (74.0%).

  • “Total Functional Capacity (TFC) score of 10 or more).”

    SourceClinicalTrials.gov NCT07378644

  • “n = 845”

    SourceFurr Stimming et al. (2025)

  • “n = 1068”

    SourceFurr Stimming et al. (2025)

  • “n = 540”

    SourceFurr Stimming et al. (2025)

  • “n = 116”

    SourceFurr Stimming et al. (2025)

  • “n = 15”

    SourceFurr Stimming et al. (2025)

  • “Most participants were in TFC stages I–III, with the highest proportion (41.3%) of participants in stage II (Table 1).”

    SourceFurr Stimming et al. (2025)

• Patients entering the eligible population each year

  5.1%Range 3.5% to 13%Quoted source

  Entries are annual incidence divided by prevalence. The base case is the global pooled incidence of 0.48 per 100,000 person-years over the United States prevalence of 9.4 per 100,000: 5.1%. The low bound uses the lower confidence limit of 0.33 (3.5%). The high bound uses the United States commercial claims incidence of 1.22 (13.0%), from a study that required no look-back period before a first claim and can therefore count an existing case as new.

  • “Pooled incidence was 0.48 cases per 100,000 person-years (95% CI, 0.33-0.63).”

    SourceMedina et al. (2022)

  • “We estimated a cumulative age-adjusted HD frequency rate of 6.52 per 100,000 persons and a cumulative incidence rate of 1.22 per 100,000 person years.”

    SourceBruzelius et al. (2019)

• Patients leaving the eligible population each year

  5.6%Range 4.6% to 6.5%Quoted source

  Exits are deaths. A constant annual rate fitted to a median survival of 12.4 years from first recorded diagnosis is ln(2) / 12.4 = 5.6%. The bounds use the 95% confidence interval of the median: ln(2) / 15.2 = 4.6% and ln(2) / 10.6 = 6.5%. The cohort is from United Kingdom primary care; no United States study of survival from diagnosis was found.

  • “The KM survival curve (Figure 1) shows a median survival time of 12.4 years (95% CI 10.6–15.2).”

    SourceFurby et al. (2022)

• SKY-0515 cost per patient per year (placeholder)

  $318,750Range $207,188 to $375,000Assumption

  No price has been published, so this value is a placeholder. The base case is the annual cost that a published United States cost-effectiveness analysis assumed for tominersen, an intrathecal huntingtin-lowering therapy: three injections per year at $106,250 each, a price taken from a spinal muscular atrophy treatment after a 15% payer discount ($318,750). The bounds are that analysis's sensitivity range ($207,188 to $375,000), and the high bound is the cost before the discount. The high bound is also close to the annual cost stated at launch for two oral drugs for rare neurological diseases: Skyclarys ($370,000 wholesale acquisition cost) and Daybue (about $375,000 average net cost to payers). The model counts a year as 365.25 days, so the drug cost per patient per year in the results is $318,968. A plan replaces the value when a price is published.

  • “Since Tominersen and AMT-130 are currently in clinical trials, we lacked established cost data and therefore relied on cost estimates from treatments for spinal muscular atrophy (SMA).”

    SourcePatil et al. (2026)

  • “After accounting for the discount, the estimated cost of a single 60 mg injection of Tominersen was $106,250.”

    SourcePatil et al. (2026)

  • “Based on this schedule, the estimated annual cost of Tominersen was $318,750.”

    SourcePatil et al. (2026)

  • “$207,188–375,000”

    SourcePatil et al. (2026)

  • “Furthermore, the DMTs currently under development vary in mechanism of action (small molecule, ASO, gene therapy), route of administration (oral, intrathecal, intraparenchymal), and once vs recurrent therapy; these contingencies make it difficult at this time to assign a DMT price in our exploratory analysis.”

    SourceGuzauskas et al. (2024)

  • “Reata announced that Skyclarys would have a wholesale acquisition price of $370,000 annually.”

    SourceDrug Discovery and Development (2023)

  • “The list price of Daybue will be $21.10 per milliliter, or an estimated average net realized cost to payors of about $375,000 annually”

    SourceManaged Healthcare Executive (2023)

• Days the SKY-0515 cost covers

  365 daysAssumption

  The drug cost is entered per patient per year, so the cost covers 365 days. A plan entering a pack price sets the days one pack supplies.

• SKY-0515 adherence

  100%Assumption

  No adherence data for SKY-0515 outside a trial exist. The base case assumes the drug is supplied on every day of treatment, which gives the highest drug cost per treated patient.

• Comprehensive metabolic panel, cost per test

  $10.56Published data

  The national limit amount for CPT 80053 in the Medicare Clinical Laboratory Fee Schedule for the fourth quarter of 2026.

  • PUF_CLFS_CY2026_Q4V1.csv, HCPCS 80053 (Comprehen metabolic panel), RATE 10.56

    SourceCMS Clinical Laboratory Fee Schedule (2026)

• Complete blood count with differential, cost per test

  $7.77Published data

  The national limit amount for CPT 85025 in the Medicare Clinical Laboratory Fee Schedule for the fourth quarter of 2026.

  • PUF_CLFS_CY2026_Q4V1.csv, HCPCS 85025 (Complete cbc w/auto diff wbc), RATE 7.77

    SourceCMS Clinical Laboratory Fee Schedule (2026)

• Neurology office visit, cost per visit

  $135.61Range $95.19 to $192.39Published data

  The Medicare Physician Fee Schedule national non-facility amount for CPT 99214 in the October 2026 release: 4.06 total relative value units x the conversion factor of 33.4009 = $135.61. The bounds are CPT 99213 (2.85 units, $95.19) and CPT 99215 (5.76 units, $192.39).

  • PPRRVU2026_Oct_nonQPP.csv, HCPCS 99214 (Office o/p est mod 30 min), non-facility total RVU 4.06, conversion factor 33.4009

    SourceCMS Physician Fee Schedule Relative Value File (2026)

  • PPRRVU2026_Oct_nonQPP.csv, HCPCS 99213 (Office o/p est low 20 min), non-facility total RVU 2.85; HCPCS 99215 (Office o/p est hi 40 min), non-facility total RVU 5.76

    SourceCMS Physician Fee Schedule Relative Value File (2026)

• Comprehensive metabolic panel schedule, SKY-0515 with standard of care

  Every 3 monthsAssumption

  No label exists, so the schedule is an assumption. The phase 2/3 study record names blood tests among its assessments without a frequency; one panel every 3 months is assumed.

  • “Safety and efficacy will be evaluated through blood tests, imaging (MRI), and clinical assessments, including the Unified Huntington's Disease Rating Scale (UHDRS).”

    SourceClinicalTrials.gov NCT07378644

• Complete blood count with differential schedule, SKY-0515 with standard of care

  Every 3 monthsAssumption

  No label exists, so the schedule is an assumption. The phase 2/3 study record names blood tests among its assessments without a frequency; one count every 3 months is assumed.

  • “Safety and efficacy will be evaluated through blood tests, imaging (MRI), and clinical assessments, including the Unified Huntington's Disease Rating Scale (UHDRS).”

    SourceClinicalTrials.gov NCT07378644

• Neurology office visit schedule, SKY-0515 with standard of care

  Every 6 monthsAssumption

  One prescriber visit every 6 months is assumed for a patient on SKY-0515. In a Colorado all-payer claims study 49.9% of people with Huntington's disease saw a neurologist in a calendar year, so for about half of treated patients these visits may already occur and the visit cost is an upper estimate.

  • “Approximately half (49.9%) received neurologist care, with 33.8% seeing a MDS during the given calendar year.”

    SourceOgilvie et al. (2026)

• Market share

  Assumption

  SKY-0515 is not marketed, so every share is an assumption. No disease-modifying therapy for Huntington's disease is approved, so the mix without SKY-0515 is standard of care alone. With SKY-0515, 10%, 20%, and 30% of eligible patients are assumed to be on it in years 1 to 3. Each share is the average share of eligible patients on SKY-0515 over the year, in patient-years, so a patient who starts at mid-year counts as half a patient, and discontinuation is part of the share. The increase of 10 percentage points per year is half the 20% per year of the ICER reference case, and the year 3 share stays below the 49.9% of people with Huntington's disease who saw a neurologist in a calendar year.

  • “Assume an equal proportion of patients (20%) are treated each year over five years, arriving at cumulative 100% at five years.”

    SourceICER reference case (2025)

  • “Approximately half (49.9%) received neurologist care, with 33.8% seeing a MDS during the given calendar year.”

    SourceOgilvie et al. (2026)

Methods and limitations

Methods

• The model follows the ISPOR budget impact analysis good practice report (Sullivan et al., 2014): a health plan perspective, results for each of 3 years, and undiscounted costs.
• The population is prevalent and open. The funnel gives the eligible members in year 1; each later year adds the patients entering (incidence over prevalence) and removes those leaving (deaths).
• SKY-0515 is modeled as an addition to standard of care. The phase 1/2 study of SKY-0515 permitted stable treatment for Huntington's disease, and no disease-modifying therapy is approved, so the mix without SKY-0515 is standard of care alone.
• Each patient on SKY-0515 in a year is costed for 12 months of drug and monitoring.
• Costs that are equal in both mixes, including symptomatic treatment such as VMAT2 inhibitors and the medical care of Huntington's disease, are left out. The total without SKY-0515 is therefore $0, and the budget impact equals the spending on SKY-0515 and its monitoring.
• The one-way sensitivity analysis moves each input between bounds taken from a confidence interval, a range across sources, a published sensitivity range, or adjacent billing levels, as that input's rationale states.

Limitations

• The SKY-0515 price is a placeholder. SKY-0515 is not approved in any country and no price has been published; the result scales in proportion to the price entered.
• No source reports the share of diagnosed patients with a Total Functional Capacity score of 10 or more. The base case interpolates within stage II of a research registry in which 5.1% of participants were in stages IV and V. In United States claims the share classified as early stage was 53.7% in a database of commercial, Medicaid, and Medicare Supplemental members and 23.4% (139 of 595) in Medicaid. Claims algorithms and Total Functional Capacity stages classify patients differently, so these figures indicate direction only: the share in a plan population may be lower than the base case, most of all in a Medicaid plan.
• The share genetically confirmed with 40 or more CAG repeats is set to 100% because no source reports it.
• Entries and exits are rates for all diagnosed patients applied to the eligible population, which holds the stage mix constant: patients whose function falls below the criterion are assumed to be replaced by newly eligible patients. If patients continue SKY-0515 after their function falls below the criterion, the number treated is higher than shown.
• Survival from diagnosis is from a United Kingdom cohort.
• Market shares are assumptions. No uptake data exist for a disease-modifying therapy in Huntington's disease.
• No medical cost offset is counted. No placebo-controlled efficacy result for SKY-0515 has been reported.
• AMT-130, a one-time gene therapy for which a marketing application was submitted to the FDA in September 2026, is absent from both mixes; a prevalent model cannot cost a one-time treatment. If it is approved and SKY-0515 displaces it, the budget impact is lower than shown.
• People who carry the gene expansion without a clinical diagnosis are outside the population. Coverage of that group would raise the eligible population.
• Adverse event costs, brain MRI, and the cost of a confirmatory genetic test are left out.