The goal of this clinical trial was to compare transdermal glomerular filtration rate (tGFR) to plasma-derived indexed GFR (nGFR) using MB-102 (relmapirazin) as the fluorescent compound. Adults with kidney function ranging from estimated glomerular filtration rate (eGFR) <120 to >15 mL/min/1.73 m2 and spanning the entire range of human skin colors as defined by the Fitzpatrick Skin Scale (FSS) were included in the study.

The main questions that the study aimed to answer were:

• To establish that the MB-102 transdermal fluorescence assessed GFR using the MediBeacon Transdermal GFR System with the TGFR reusable sensor with disposable adhesive ring was comparable to the measured MB-102 plasma GFR.
• To evaluate the safety and effectiveness of the MediBeacon Transdermal GFR System and the TGFR reusable sensor with disposable adhesive ring for the non-invasive transdermal fluorescence detection of MB-102 in participants

On dosing day, participants had the TGFR reusable sensor with disposable adhesive ring placed on their chest, and the MediBeacon Transdermal GFR System initiated to collect background fluorescence. When this was completed, participants then received a single dose of MB-102. Blood samples were collected and fluorescent measurements were taken over a 12- or 24-hour (or longer) period, depending upon enrollment group. For those with significant renal compromise, fluorescent measurements were continued until the sensor no longer detected MB-102 in the body. Following completion of the treatment period, participants returned to the study center approximately 1 week later for a safety follow-up visit. Researchers compared the results to see if the transdermal GFR measurements were comparable to the measured plasma GFR.

Inclusion Criteria:

• Eligible female non-pregnant participants who are either not of child-bearing potential or willing to use adequate contraception during the trial
• Males must be willing to practice abstinence or utilize adequate contraception from dosing day to at least 7 days post-dose
• For women of childbearing potential, the participant should have a negative serum pregnancy test at screening, and agrees to one of the following acceptable contraceptive methods used consistently and correctly i.e. abstinence, oral contraceptive either combined or progesterone alone; injectable progesterone, implants of levonorgestrel, estrogenic vaginal ring, percutaneous contraceptive patches, IUD device or system or male partner sterilization
• Men will not donate sperm during the study and for 1 month following the last dose of study drug.
• Participants who are capable of directly providing informed consent and who can comply with the requirements and restrictions required by the protocol
• Adequate venous access sufficient to allow blood sampling per protocol requirements

Exclusion Criteria:

• Participants positive for COVID-19 at the time of dosing
• Recent donation or loss of blood or plasma: 100 mL to 499 mL within 30 days prior to the initial dose of the study medication; or more than 499 mL within 56 days prior to the initial dose of study medication
• Non-steroidal anti-inflammatory (NSAID) use within 3 days of MB-102 dosing
• The participant has participated in a clinical trial and has received an investigational product within the following time ranges: prior to the first dosing day in the current study: either 30 days or 5 half-lives of the investigational product (whichever duration is longer).
• History of skin sensitivity to adhesives (e.g. Band-Aids, surgical tape)
• History of severe allergic hypersensitivity reactions (unacceptable adverse events) or anaphylactoid reaction to any allergen including drugs, MB-102 or other related products (intolerance to a drug is not considered a drug allergy).
• Any characteristics which, in the opinion of the investigator, makes the participant a poor candidate for participation in the clinical trial
• Significant scaring, tattoos or alterations in pigmentation on the sternum or other sensor location testing areas that would alter sensor readings versus other areas of the skin
• Use of tanning sprays, tanning products etc. on the upper chest within 2 weeks of dosing day
• Use make-up, lotions, Vaseline or other products on the area of the upper chest on the day prior to or the day of dosing
• Any serious or uncontrolled medical disorder, active infection, physical exam finding, laboratory finding, or psychiatric condition that in the opinion of the investigator would limit the participant's ability to complete study requirements or may put the participant at increased risk or compromise the interpretability of study results.
• Currently receiving dialysis
• Currently anuric
• Positive serum pregnancy test
• Participants with an eGFR > 120 mL/min/1.73m^2