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X-linked HypophosphatemiaPhase 1/2NCT06525636

A First-in-human Study of KK8123 in Adults With X-linked Hypophosphatemia

A Phase 1/2 study testing KK8123 in people with X-linked Hypophosphatemia, run by Kyowa Kirin Co., Ltd. at 10 sites in 5 countries.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
Search all trials

Trial summary

A first-in-human study of KK8123 in adults with X-linked hypophosphatemia. Read more about this study

Who is it for?
Ages 18 to 65 years
Conditions the study is for
X-linked Hypophosphatemia
What is being tested?
KK8123
Type of treatment
Injection or infusion
Could I receive a placebo?
No, everyone receives an active treatment
How many people
39 participants
Where
10 sitesin 5 countries
Study dates
9 Oct 2024to 14 Jun 2030
Phase
Phase 1/2
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 to 65 years
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Part 1: Inclusion Criteria:
  • Male or female patients aged 18 to 65 years inclusive at the time of signing the ICF.
  • Body weight is at least 40 kg.
  • Diagnosed with XLH (as documented by the investigator).
  • Have a value of fasting serum phosphorus < 2.5 mg/dL (0.81 mmol/L) at Screening.
  • Have a value of renal TmP/GFR < 2.5 mg/dL (0.81 mmol/L) at Screening.
Show all 16Show fewer
  • eGFR ≥ 60 mL/min (using the Chronic Kidney Disease Epidemiology Collaboration equation [Inker, 2021]) at Screening.
  • Have a corrected serum calcium level < 10.8 mg/dL (2.7 mmol/L) at Screening.
  • Provide a signed ICF.
  • Agree not to change diet and exercise regimen from one week prior to dosing to end of study.
  • Have a negative pregnancy test at Screening and be willing to have additional pregnancy tests during the study (female participants only).
  • If taking chronic pain medications (including narcotic pain medications/opioids), must be on a stable regimen for at least 21 days prior to the Screening visit, and be willing to maintain medications at the same stable dose(s) and schedule throughout the clinical trial. The dose must not exceed 60 mg oral morphine equivalents/day.
  • Be willing to use a method of contraception following local country guidelines while participating in the study and for 30 weeks after the last dose (all sexually active participants of childbearing potential).
  • Women of non-childbearing potential are defined as permanently sterile (i.e., due to tubal ligation at least one year before Screening, hysterectomy or bilateral oophorectomy) or postmenopausal (defined as at least 12 months post cessation of menses without an alternative medical cause).
  • Postmenopausal status of female participants will be confirmed with a Screening serum follicle-stimulating hormone level >40 mIU/mL.
  • Must, in the opinion of the investigator, be willing and able to complete all aspects of the study, adhere to the study visit schedule and comply with the assessments.

Who cannot join

  • Part 1: Exclusion Criteria:
  • For XLH participants previously treated with the applicable prior therapy, use within the protocol defined washout period prior to ICF signature.
  • Prior history of positive test for human immunodeficiency virus antibody, positive test for hepatitis B surface antigen, and/or hepatitis C virus antibody at Screening.
  • History of hypersensitivity to any ingredient of any therapeutic monoclonal antibody.
  • Have an active infection.
  • Grade 3 or greater nephrocalcinosis as confirmed by renal ultrasound.
Show all 48Show fewer
  • Uncontrolled diabetes mellitus at Screening.
  • History of known immunodeficiency.
  • History of alcoholism or drug abuse.
  • History of donation of blood within 60 days prior to Screening.
  • Use of any IP or investigational medical device within 30 days prior to Screening, or requirement for any investigational agent prior to completion of all scheduled study assessments.
  • Use of any therapeutic mAb within 90 days prior to Screening.
  • Use of pharmacologically active vitamin D, its metabolites or analogs, oral phosphate for treatment of XLH, aluminum hydroxide antacids, acetazolamide, thiazide diuretics, and/or systemic corticosteroids within 14 days prior to Screening. If the participant takes any of these medications, a washout period of 14 days will be required after signing the ICF and before any other screeening assessments begin.
  • Use of medication to suppress PTH (e.g., calcimimetics) within 2 months prior to Screening and for the duration of the study.
  • Use of denosumab within 6 months prior to Screening.
  • Use of oral bisphosphonates in the 2 years prior to Screening.
  • Use of teriparatide or abaloparatide in the 2 months prior to Screening.
  • Plasma iPTH ≥ 2.5 × ULN at Screening.
  • Planned or recommended orthopedic surgery during the study.
  • History of traumatic fracture or orthopedic surgery within 6 months prior to Screening.
  • Participants who are lactating.
  • Current active and symptomatic COVID-19 infection immediately prior to study treatment.
  • Presence or history of any condition that, in the view of the investigator, places the participant at high risk of poor treatment compliance or of not completing the study, or that would confound safety or interpretation of results.
  • Part 2: Inclusion Criteria:
  • Completion of relevant cohort in Part 1 of the study.
  • Provide a signed informed consent after the nature of Part 2 of the study has been explained.
  • Body weight is at least 40 kg.
  • Negative pregnancy test at Screening of Part 2 and willing to have additional pregnancy tests until the end of the study (female participants only).
  • If taking chronic pain medications (including narcotic pain medications/opioids), must be on a stable regimen for at least 21 days prior to Week 0 of Part 2, and be willing to maintain medications at the same stable dose(s) and schedule throughout the study. The dose must not exceed 60 mg oral morphine equivalents/day.
  • Be willing to use a method of contraception following local country guidelines while participating in the study and for 30 weeks after the last dose (all sexually active participants of childbearing potential). Women of non-childbearing potential are defined as permanently sterile (i.e., due to tubal ligation at least one year before Screening, hysterectomy or bilateral oophorectomy) or postmenopausal (defined as at least 12 months post cessation of menses without an alternative medical cause). Postmenopausal status of female participants will be confirmed with a Week 0 serum follicle-stimulating hormone level >40 mIU/mL.
  • Must, in the opinion of the investigator, be willing and able to complete all aspects of the study, adhere to the study visit schedule and comply with all the assessments.
  • For participants who complete the Part 1 EoS visit more than 30 days before starting Part 2 Week 0, eGFR ≥ 60 mL/min at Screening.
  • For participants who complete the Part 1 EoS visit more than 30 days before starting Part 2 Week 0, have a corrected serum calcium level of < 10.8 mg/dl (2.7 mmol/L) at Screening.
  • Part 2: Exclusion Criteria:
  • Use of the applicable prior therapy following completion of Part 1 of the study.
  • Have an active infection.
  • Donation of blood within 60 days prior to Week 0 of Part 2.
  • Use of any investigational product other than KK8123, or investigational medical device, within 30 days prior to Week 0 of Part 2, or requirement for any investigational agent prior to completion of all scheduled study assessments.
  • Use of any therapeutic mAb other than KK8123 within 90 days prior to Week 0 of Part 2.
  • Use of pharmacologically active vitamin D, its metabolites or analogs, oral phosphate for treatment of XLH, aluminum hydroxide antacids, acetazolamide, thiazide diuretics, and/or systemic corticosteroids within 14 days prior to Week 0 of Part 2.
  • Use of medication to suppress PTH (e.g., calcimimetics) within 2 months prior to Week 0 of Part 2.
  • Use of oral bisphosphonates following completion of Part 1 of the study.
  • Use of teriparatide or abaloparatide in the 2 months prior to Week 0 of Part 2.
  • Planned or recommended orthopedic surgery during the study.
  • History of traumatic fracture or orthopedic surgery within 6 months prior to Week 0 of Part 2.
  • Participants who are lactating.
  • Current active and symptomatic COVID-19 infection, or a history of suffering any long-term sequalae from COVID-19 infection.
  • Presence or history of any condition that, in the view of the investigator, places the participant at high risk of poor treatment compliance or of not completing the study.

Trial locations and contacts

10 sites in 5 countries. Contact the study team or a site near you to ask about taking part.

Kyowa Kirin contact

609-919-1100

KKD.Clintrial.82@kyowakirin.com

10 sites in 5 countries

United States5 sites, 5 recruiting

  • Indiana University School of Medicine University Hospital

    Indianapolis, Indiana, 46202

    Fridah Mbatia, 317-278-6123, fwmbatia@iu.edu

    Erik Imel, MD

    Recruiting

  • Vanderbilt University Medical Center

    Nashville, Tennessee, 37232

    Margo Black, MSN RN CCRP, 615-343-5846, margo.black@vumc.org

    Kathryn Dahir, MD

    Recruiting

  • Yale Center for XLH/ Yale University School of Medicine

    New Haven, Connecticut, 06510

    Elizabeth Olear, MS, MA, 203-785-6779, ycxlhinfo@yale.edu

    Clemens Bergwitz, MD

    Recruiting

  • Mayo Clinic

    Rochester, Minnesota, 55905

    Not yet recruiting

  • University of California - San Francisco

    San Francisco, California, 94158

    Farzana Perwad, 415-476-2423, farzana.perwad@ucsf.edu

    Farzana Perwad, MD

    Recruiting

Other trials in United States

Germany2 sites, 2 recruiting

  • Institute of Osteology and Biomechanics (IOBM)

    Hamburg, 22529

    Alison Schoen, 0152 2281 6702, Ali.Schoen@uke.de

    Ralf Oheim, MD

    Recruiting

  • Universitaetsklinikum Wurzburg

    Würzburg, 97074

    Jasmin Baumann, 0049 931/803-3590, jasmin.baumann@klh.de

    Lothar Seefried, MD

    Recruiting

Other trials in Germany

Canada1 site, 1 recruiting

  • Bone Research and Education Center

    Oakville, Ontario

    Jouma Malhem, 905 844 7048, jouma@boneresearch.ca

    Aliya Khan, MD

    Recruiting

Other trials in Canada

France1 site, 1 recruiting

  • Hoptial Bictre

    Le Kremlin-Bicêtre, Paris, 94275

    Guilaine Guiose, 33 1 45 21 74 53 Dect : 24119, guilaine.guiose@aphp.fr

    Peter Kamenicky, MD

    Recruiting

Other trials in France

Spain1 site, 1 recruiting

  • Hospital Universitario La Paz

    Madrid, 28046

    Darío Aguilar Rico, +34 917277193, darioaguilarrico.hulp@gmail.com

    Pilar Aguado Acin, MD

    Recruiting

Other trials in Spain

About this study

Official title: A Multicenter, Open-label, Phase 1/2, Dose-escalation and Subsequent Safety Extension Study of Subcutaneous KK8123 in Adult Patients With X-linked Hypophosphatemia

A first-in-human study of KK8123 in adults with X-linked hypophosphatemia.

Read the detailed description

Study 8123-001 is a Phase 1/2, multicenter, open-label, dose-escalation study to assess the safety, tolerability, PK and PD of KK8123, with an optional safety extension period. This study is comprised of a Screening Period followed by Part 1 and Part 2. The Screening Period will last up to 35 days (including obtaining informed consent). Part 1 is a Dose Escalation Period consisting of a nominal (planned) Treatment Period (all cohorts) followed by an Observation Period, and Part 2 is an optional Extension Period.

Being tested
KK8123
Keywords
Gene Mutation, Bone Disease, Metabolic Disease, Musculoskeletal Disease,, Rare Disease, Hypophosphatemia, Familial Renal Tubular Transport, Inborn Errors, Kidney Diseases
Medical subject headings
Familial Hypophosphatemic Rickets, Bone Diseases, Metabolic Diseases, Musculoskeletal Diseases, Rare Diseases, Hypophosphatemia, Kidney Diseases

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • KK8123Drug

    Subcutaneous administration

Study groups in NCT06525636
Study groupRoleWhat they receive
Part 1: Cohort 1ExperimentalLow Dose of KK8123
Receives: Drug: KK8123
Part 1: Cohort 2ExperimentalMid dose of KK8123
Receives: Drug: KK8123
Part 1: Cohort 3ExperimentalHigh dose of KK8123
Receives: Drug: KK8123
Part 1: Cohort 4AExperimentalMid-High dose of KK8123
Receives: Drug: KK8123
Part 1: Cohort 4BExperimentalMid-High dose of KK8123
Receives: Drug: KK8123
Part 2: Extension PhaseExperimentalMid-High dose of KK8123
Receives: Drug: KK8123

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Part 1: Number of participants with TEAEs

    Measured: For up to 48 weeks.

  2. Part 1: Percentage of participants with TEAEs

    Measured: For up to 48 weeks.

  3. Part 2: Number of participants with TEAEs

    Measured: For up to 48 weeks.

  4. Part 2: Percentage of participants with TEAEs

    Measured: For up to 48 weeks.

  5. Part 1: Change from baseline for haematology laboratories values

    Measured: For up to 48 weeks.

  6. Part 2: Change from baseline for haematology laboratories values

    Measured: For up to 48 weeks.

  7. Part 1: Change from baseline for clinical chemistry laboratories values

    Measured: For up to 48 weeks.

  8. Part 2: Change from baseline for clinical chemistry laboratories values

    Measured: For up to 48 weeks.

  9. Part 1: Change from baseline in continuous variables for FSH

    Measured: For up to 48 weeks.

  10. Part 2: Change from baseline in continuous variables for FSH

    Measured: For up to 48 weeks.

  11. Part 1: Change from baseline in continuous variables for estradiol

    Measured: For up to 48 weeks.

  12. Part 2: Change from baseline in continuous variables for estradiol

    Measured: For up to 48 weeks.

  13. Part 1: Change from baseline in continuous variables for temperature

    Measured: For up to 48 weeks.

  14. Part 2: Change from baseline in continuous variables for temperature

    Measured: For up to 48 weeks.

  15. Part 1: Change from baseline in continuous variables for pulse rate

    Measured: For up to 48 weeks.

  16. Part 2: Change from baseline in continuous variables for pulse rate

    Measured: For up to 48 weeks.

  17. Part 1: Change from baseline in continuous variables for respiratory rate

    Measured: For up to 48 weeks.

  18. Part 2: Change from baseline in continuous variables for respiratory rate

    Measured: For up to 48 weeks.

  19. Part 1: Change from baseline in continuous variables for systolic and diastolic blood pressure

    Measured: For up to 48 weeks.

  20. Part 2: Change from baseline in continuous variables for systolic and diastolic blood pressure

    Measured: For up to 48 weeks.

  21. Part 1: Change from baseline in continuous variables for QT

    Measured: For up to 48 weeks.

  22. Part 2: Change from baseline in continuous variables for QT

    Measured: For up to 48 weeks.

  23. Part 1: Change from baseline in continuous variables for QTc

    Measured: For up to 48 weeks.

  24. Part 2: Change from baseline in continuous variables for QTc

    Measured: For up to 48 weeks.

  25. Part 1: Change from baseline in continuous variables for QTCF

    Measured: For up to 48 weeks.

  26. Part 2: Change from baseline in continuous variables for QTCF

    Measured: For up to 48 weeks.

  27. Part 1: Change from baseline in continuous variables for QRS

    Measured: For up to 48 weeks.

  28. Part 2: Change from baseline in continuous variables for QRS

    Measured: For up to 48 weeks.

  29. Part 1: Change from baseline in continuous variables for heart rate

    Measured: For up to 48 weeks.

  30. Part 2: Change from baseline in continuous variables for heart rate

    Measured: For up to 48 weeks.

  31. Part 1: The presence or absence of abnormality on ectopic mineralization, any sign of left ventricular hypertrophy or heart failures before and after administration of KK8123 on Echocardiogram

    Measured: For up to 48 weeks.

  32. Part 2: The presence or absence of abnormality on ectopic mineralization, any sign of left ventricular hypertrophy or heart failures before and after administration of KK8123 on Echocardiogram

    Measured: For up to 48 weeks.

  33. Part 1: Before and after administration presented at each time point in categorical variables for renal ultrasound

    Measured: For up to 48 weeks.

  34. Part 2: Before and after administration presented at each time point in categorical variables for renal ultrasound

    Measured: For up to 48 weeks.

  35. Part 1: KK8123 concentrations by maximum plasma concentration (Cmax)

    Measured: For up to 48 weeks.

  36. Part 2: KK8123 concentrations by maximum plasma concentration (Cmax)

    Measured: For up to 48 weeks.

  37. Part 1: KK8123 concentrations by maximum serum concentration (tmax)

    Measured: For up to 48 weeks.

  38. Part 2: KK8123 concentrations by maximum serum concentration (tmax)

    Measured: For up to 48 weeks.

  39. Part 1: KK8123 concentrations by area under the serum concentration time curve from zero to last detectable time point (AUClast)

    Measured: For up to 48 weeks.

  40. Part 2: KK8123 concentrations by area under the serum concentration time curve from zero to last detectable time point (AUClast)

    Measured: For up to 48 weeks.

  41. Part 1: KK8123 concentrations by the area under the serum concentration time curve from zero to infinity (AUC00-inf)

    Measured: For up to 48 weeks.

  42. Part 2: KK8123 concentrations by the area under the serum concentration time curve from zero to infinity (AUC00-inf)

    Measured: For up to 48 weeks.

  43. Part 1: KK8123 concentrations by apparent volume of distribution (V/F)

    Measured: For up to 48 weeks.

  44. Part 2: KK8123 concentrations by apparent volume of distribution (V/F)

    Measured: For up to 48 weeks.

  45. Part 1: KK8123 concentrations by terminal half-life (t1/2)

    Measured: For up to 48 weeks.

  46. Part 2: KK8123 concentrations by terminal half-life (t1/2)

    Measured: For up to 48 weeks.

  47. Part 1: KK8123 concentrations by apparent clearance (CL/F)

    Measured: For up to 48 weeks.

  48. Part 2: KK8123 concentrations by apparent clearance (CL/F)

    Measured: For up to 48 weeks.

  49. Part 1: KK8123 concentrations by maximum plasma concentration steady state (Cmax,ss)

    Measured: For up to 48 weeks.

  50. Part 2: KK8123 concentrations by maximum plasma concentration steady state (Cmax,ss)

    Measured: For up to 48 weeks.

  51. Part 1: KK8123 concentrations by time to maximum serum concentration steady state (tmax,ss)

    Measured: For up to 48 weeks.

  52. Part 2: KK8123 concentrations by time to maximum serum concentration steady state (tmax,ss)

    Measured: For up to 48 weeks.

  53. Part 1: KK8123 concentrations over time by area under the serum concentration curve within a dosing interval at steady state (AUCtau,ss)

    Measured: For up to 48 weeks.

  54. Part 2: KK8123 concentrations over time by area under the serum concentration curve within a dosing interval at steady state (AUCtau,ss)

    Measured: For up to 48 weeks.

  55. Part 1: KK8123 concentrations by time to steady state

    Measured: For up to 48 weeks.

  56. Part 2: KK8123 concentrations by time to steady state

    Measured: For up to 48 weeks.

  57. Part 1: KK8123 concentrations by accumulation ratio

    Measured: For up to 48 weeks.

  58. Part 2: KK8123 concentrations by accumulation ratio

    Measured: For up to 48 weeks.

  59. Part 1: To evaluate the effect of single and multiple SC administrations of KK8123 on serum phosphorus levels

    Measured: For up to 48 weeks.

  60. Part 2: To evaluate the effect of multiple SC administrations of KK8123 on serum phosphorus levels

    Measured: For up to 48 weeks.

Secondary outcomes (4)

  1. Part 1: ADA positivity titers to be assessed by absolute number

    Measured: For up to 48 weeks.

  2. Part 1: ADA positivity titers to be assessed by percentage

    Measured: For up to 48 weeks.

  3. Part 2: ADA positivity titers to be assessed by absolute number

    Measured: For up to 48 weeks.

  4. Part 2: ADA positivity titers to be assessed by percentage

    Measured: For up to 48 weeks.

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted29 Jul 2024
  2. Study start9 Oct 2024
  3. Primary completion14 Jun 2030 (estimated)
  4. Study completion14 Jun 2030 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 1/2
Primary purpose
Treatment
Allocation
Non-randomised
Intervention model
Sequential
Masking
None (open label)
Enrolment
39 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT06525636
Sponsor's protocol ID
8123-001
Status last verified
Nov 2026
First submitted
10 May 2024
Last updated
6 Nov 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No

Questions about this trial

What is this clinical trial studying?

A Phase 1/2 study testing KK8123 in people with X-linked Hypophosphatemia, run by Kyowa Kirin Co., Ltd. at 10 sites in 5 countries.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 16 inclusion and 48 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 6 Nov 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 10 sites in United States, Germany, Canada, France, Spain. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this combined phase mean?

Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Kyowa Kirin (609-919-1100, KKD.Clintrial.82@kyowakirin.com), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Part 1: Number of participants with TEAEs (time frame: For up to 48 weeks.). The study lists 60 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT06525636.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 6 Nov 2026.

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