Abstract
Objective
Current treatments for Friedreich's ataxia, a neurodegenerative disorder characterized by decreased intramitochondrial frataxin, do not address low frataxin concentrations. Nomlabofusp (previously CTI‐1601) is a frataxin replacement therapy with a unique mechanism of action that directly addresses this underlying frataxin deficiency. Phase 1 studies assessed the safety, pharmacokinetic, and pharmacodynamic profiles of subcutaneously administered nomlabofusp in adults with Friedreich's ataxia.
Methods
Patients were enrolled in two Phase 1, double‐blind, placebo‐controlled studies. The single ascending‐dose (SAD) study (NCT04176991) evaluated single doses of nomlabofusp (25, 50, 75, or 100 mg) or placebo. The multiple ascending‐dose (MAD) study (NCT04519567) evaluated nomlabofusp (25 mg daily for 4 days then every third day, 50 mg daily for 7 days then every 2 days, or 100 mg daily) or placebo for 13 days.
Results
Patients aged 19–69 years were enrolled (SAD, N = 28; MAD, N = 27). Nomlabofusp was generally well tolerated through 13 days. Most adverse events were mild and resolved quickly. No serious adverse events or deaths were reported. Peak nomlabofusp plasma concentrations occurred 15 min after subcutaneous administration. Nomlabofusp plasma exposures increased with increasing doses and daily administration and decreased with reduced dosing frequency. Increased frataxin concentrations were observed in buccal cells, skin, and platelets with higher and more frequent nomlabofusp administration.
Interpretation
Results from this study support a favorable safety profile for nomlabofusp. Subcutaneous nomlabofusp injections were quickly absorbed; higher doses and daily administration resulted in increased tissue frataxin concentrations. Future studies will evaluate longer‐term safety and possible efficacy of nomlabofusp.
Introduction
Friedreich's ataxia (FRDA) is a rare, autosomal recessive, progressive, multisystem disease that affects the cardiac, endocrine, and central nervous systems. The prevalence of FRDA has been estimated to be between 1:20,000 and 1:125,000, affecting male and female patients with equal frequency. 1 , 2 , 3 Disease onset typically begins in childhood, and most patients diagnosed in childhood become wheelchair dependent within 10–15 years of diagnosis. 3 , 4 , 5 Patients experience progressive neurologic lower and upper limb dysfunction, and FRDA leads to quality of life impairment and early mortality in a majority of individuals. 3 , 4 Other manifestations may include dysarthria, visual disturbances, loss of hearing, and diabetes. 3 , 4
FRDA is the most common inherited ataxia and is almost exclusively (97%) caused by biallelic guanine‐adenine‐adenine (GAA) triplet expansion in the FXN gene. 6 The GAA triplet expansion, which can range from 70 to 1700 repeats in both alleles in patients with FRDA, causes transcriptional repression of the FXN gene with longer GAA repeat length associated with lower FXN expression. 1 , 6 , 7 Frataxin protein concentrations in patients with FRDA are approximately 2%–30% of those seen in normal controls, depending on the tissue type analyzed. 7 Age at onset, severity of clinical symptoms, and cardiomyopathy correlate with GAA repeat number, with higher repeat numbers associated with earlier onset and more severe disease. 2 , 6 Heterozygous carriers typically have frataxin concentrations at approximately 50% of normal concentrations but are phenotypically normal. 6 , 7 Currently, there are no treatment options that address the core deficit of FRDA, which is low concentrations of frataxin. Proposed therapeutics should maintain function, slow the loss of motor control and deterioration of motor function, and delay the other clinical manifestations of FRDA.
Nomlabofusp (previously known as CTI‐1601; CAS 2548202‐05‐5) is a novel, recombinant fusion protein with a short cationic cell‐penetrant peptide fused to the amino‐terminus of the complete human frataxin protein, which consists of a mitochondrial‐targeting sequence followed by mature frataxin (Fig. 1). Designed to deliver human frataxin into mitochondria and increase mitochondrial frataxin, nomlabofusp is being developed as a novel and specific frataxin therapy to supplement deficient endogenous frataxin in adults and children with FRDA and is the first potential therapy to address the core mitochondrial deficiency of the disease. Here we describe the safety, pharmacokinetic (PK), and pharmacodynamic (PD) profiles of subcutaneous (SC) administration of single ascending doses (SADs) and multiple ascending doses (MADs) of nomlabofusp in adults with FRDA.
Figure 1.
Nomlabofusp structure. Nomlabofusp is a recombinant fusion protein consisting of a cell‐penetrant peptide (CPP) that maintains the cleavage site between the mitochondrial‐targeting sequence (MTS) and mature human frataxin present in endogenous frataxin; this allows for the CPP and MTS to be removed by mitochondrial processing peptidase (MPP) to produce mature human frataxin in the mitochondria.
Methods
Single ascending‐dose study design
The SAD study (NCT04176991) was a Phase 1, double‐blind, placebo‐controlled study comprised of a screening period (≤28 days), treatment period (1 day), and nontreatment/follow‐up period (30 days) (Fig. 2). Sentinel dosing was used for all cohorts. Randomization was assigned via an electronic data capture randomization and trial supply management module, and all patients remained blinded throughout the study. Six to eight patients were randomized 4:2 (first six patients) or 1:1 (additional patients) to each of four cohorts to receive a single SC dose of nomlabofusp (25 mg, 50 mg, 75 mg, or 100 mg) or placebo. The first two sentinel patients in each dose cohort were randomized 1:1 to receive nomlabofusp or placebo, dosed at least 1 h apart and monitored for safety. At least 24 h after the first two sentinel patients were dosed, the remaining patients were assigned to receive nomlabofusp or placebo. After the screening period, patients in the 25 and 50 mg cohorts resided at the clinical research unit (CRU) for 5 days/4 nights; after discharge, patients were contacted by phone daily and returned to the CRU for a follow‐up visit at Day 7. Patients in the 75 and 100 mg cohorts resided at the CRU for up to 13 days/12 nights, and the Day 7 follow‐up visit occurred while they were residing at the CRU.
Figure 2.
Single and multiple ascending‐dose study design. Available blinded safety data and pharmacokinetic data for each cohort were reviewed before the subsequent cohort was dosed. aSentinel dosing was employed for all cohorts. The first two sentinel patients in each dose group were randomized 1:1 to receive either nomlabofusp or placebo, dosed at least 1 h apart and monitored for safety. At least 24 h after the first two sentinel patients were dosed, the remaining patients were randomized, ensuring at least a 4:2 allocation ratio of nomlabofusp to placebo. bPatients were randomized to ensure a minimum of eight patients were enrolled per cohort in a 6:2 allocation ratio of nomlabofusp to placebo. SC, subcutaneous.
The SAD study was conducted between December 11, 2019, and October 31, 2020, in a single CRU. Recruitment of patients in the first two SAD study cohorts was completed before the study was paused on March 17, 2020, due to the COVID‐19 pandemic. No patients were active in the CRU at the time of the pause. Mitigations were established based on evolving FDA and CDC guidelines, and the study resumed on June 24, 2020. Patients in the nomlabofusp 75 and 100 mg dose cohorts were enrolled or rescreened under new protocol amendments to ensure patient safety; amendments included COVID‐19 screening and tests, modifications to clinic confinement period to limit travel, and allowance of telehealth screening and remote nursing and monitoring visits.
Multiple ascending‐dose study design
The MAD study (NCT04519567) was a Phase 1, double‐blind, placebo‐controlled study comprised of a screening period (≤28 days), treatment period (13 days), and follow‐up period (30 days). Patients who completed the SAD study were eligible to enroll in the MAD study. Randomization was assigned via an electronic data capture randomization and trial supply management module, and all patients remained blinded throughout the study. Eight to 10 patients were randomized 6:2 (first eight patients) or 1:1 (additional patients) to each of three cohorts to receive SC nomlabofusp (25 mg, 50 mg, or 100 mg) or placebo. After the screening period, patients resided at the CRU for up to 22 days/21 nights. Patients in the 25 mg MAD cohort received nomlabofusp or placebo once a day for the first 4 days followed by one dose every third day for a total of seven doses. The 50 mg MAD cohort received nomlabofusp or placebo once a day for the first 7 days followed by one dose every other day for a total of 10 doses. Patients in the 100 mg MAD cohort received nomlabofusp or placebo once a day for 13 days for a total of 13 doses. After discharge, patients were followed up by a visiting nurse on approximately Days 19 (50 and 100 mg cohorts only), 22, and 43.
The MAD study was conducted between July 31, 2020, and March 16, 2021, at a single CRU. The MAD study protocol was amended to ensure patient safety during the COVID‐19 pandemic as described above.
Patient population
Patients were eligible to participate in both the SAD and MAD studies if they were aged ≥18 years with a genetically confirmed diagnosis of FRDA caused by homozygous GAA repeat expansions. Patients were required to have a modified FRDA Rating Scale‐neurological subscale (mFARS_neuro) score ≥20 and be able to traverse a distance of 25 feet with or without an assistive device (including a wheelchair). Patients were ineligible for participation if they had any condition, disease, or situation that, based on the investigator's judgment, could confound the study results or put the patient at undue risk. Patients who experienced a serious, severe, or clinically significant adverse event (AE) in the SAD study were ineligible to enroll in the MAD study.
Assessments
Safety evaluations included incidences of AEs, serious AEs, and treatment‐related AEs; reviews of laboratory data; measurements of vital signs; examinations of electrocardiograms and echocardiograms; completion of the Columbia‐Suicide Severity Rating Scale(C‐SSRS); and physical examinations performed during the treatment and follow‐up periods. Injection sites were periodically assessed (6 h after each dose and then every 12 h for 48 h or until the next dose injection). Each injection site assessment included ranking pain on a visual analog scale, measuring the area of swelling and redness (if present), and noting any tenderness to touch.
For the PK analyses, blood samples were collected predose; at 2 (SAD only), 5, 15, and 30 min postdose; and at 1, 2, 4, 6, 12, 24, and 48 h postdose. PK parameters evaluated included maximum concentration in a dosing interval (C max), time of last quantifiable concentration in dosing interval (t last), time to maximum concentration (t max), and area under the plasma concentration‐time curve from time 0 to t last (AUClast). The PD effect of nomlabofusp, assessed in the MAD study, was defined as the increases in tissue frataxin concentrations measured in buccal cells collected via cheek swabs, skin tissue collected via punch biopsy, and platelets.
Nomlabofusp and frataxin quantification
Nomlabofusp (in plasma) and mature human frataxin (in tissue) were quantified using liquid chromatography coupled with tandem mass spectrometry. A preservative (Protease Inhibitor Cocktail, Sigma cat no. P8340) was added to whole blood collection tubes within 6 h before sample collection. Blood samples were stored at room temperature after collection and processed to plasma within 1 h. The harvested plasma was kept at −80°C. Plasma sample pretreatment involved the affinity purification extraction of nomlabofusp from 200 μL of human plasma. Nomlabofusp with stable isotope‐labeled amino acids (SILAC) or SILAC nomlabofusp was used as the internal standard. The extracted proteins were enzymatically digested to peptides. A peptide (SGT peptide or SGTLGHPGSLDETTYER) was identified and quantified using a Shimadzu Nexera X2 ultra‐high‐performance liquid chromatography (UHPLC) system coupled with a Sciex API 6500+ mass spectrometer. The calibration range of the plasma method was 0.400 to 40.0 ng/mL; samples with results above the upper limit of quantitation were diluted and reassessed. Concentrations were calculated using peak area ratios, and the linearity of the calibration curve was determined using a weighted (1/x) linear (y = mx + b) least squares regression analysis for nomlabofusp.
The plasma bioanalytical method validation was conducted in accordance with the FDA Guidance for Industry, Bioanalytical Method Validation (May 2018), 8 and European Medicines Agency Guideline on Bioanalytical Method Validation EMEA/CHMP/EWP/192217/2009 Rev.1 Corr. 2, effective February 2012. 9 Selectivity, sensitivity, linearity, accuracy, precision, matrix effect, and dilution integrity were evaluated during the validation and met FDA and EMA guidance‐suggested criteria. Stability of nomlabofusp in human plasma was evaluated in the validation, and results confirmed that nomlabofusp is stable in whole blood for up to 1 h at 4°C and the protein is stable in plasma for up to 25 h at 4°C. The analyte was demonstrated to be stable after up to three freeze/thaw cycles from −80 to 4°C. The long‐term storage stability of plasma samples was established for up to 250 days at −80°C.
Human tissue samples were homogenized and stored at −80°C. A preservative (Protease Inhibitor Cocktail Sigma cat no. P8340) was added to all matrix lots during tissue homogenization. Sample pretreatment involved the affinity purification extraction of frataxin from 250 μL of human tissue homogenate. SILAC nomlabofusp was added during the extraction as the internal standard. The extracted proteins were enzymatically digested to peptides. The SGT peptide and the GGM peptide (GGMWTLGR) were identified and quantified using a Shimadzu Nexera X2 UHPLC system coupled with a Sciex API 6500+ mass spectrometer. The SGT peptide is located at the n‐terminus of mature human frataxin and thus provides quantitation of all molecules containing human frataxin, including both baseline and additional mature human frataxin as well as nomlabofusp. The GGM peptide comprises part of the linker fusing the cell‐penetrant peptide to full‐length frataxin and is, therefore, specific to nomlabofusp; this peptide provides quantitation of intact and partially processed nomlabofusp and is not detected when nomlabofusp is fully matured to human frataxin. The calibration range of the tissue method was 0.250 to 50.0 ng/mL. Concentrations were calculated using peak area ratios and the linearity of the calibration curve was determined using a weighted (1/x) linear (y = mx + b) least squares regression analysis for human frataxin. Total protein of the tissue homogenate was measured (Pierce BCA Protein Kit, Thermo Fisher Scientific) and used to normalize the tissue frataxin concentration.
The human tissue bioanalytical methods were validated in accordance with FDA Guidance for Industry, Bioanalytical Method Validation (May 2018), 8 and EMA Guideline on Bioanalytical Method Validation EMEA/CHMP/EWP/192217/2009 Rev.1 Corr. 2, effective February 2012. 9 Selectivity, sensitivity, linearity, accuracy, precision, matrix effect, and dilution integrity were evaluated during the validation and met FDA and EMA guidance‐suggested criteria. Stability of nomlabofusp in human homogenates was evaluated in the validation, and results confirmed that nomlabofusp is stable in tissue homogenate for up to 9.5 h at 4°C. The protein was demonstrated to be stable after up to three freeze/thaw cycles from −80 to 4°C. The long‐term storage stability of tissue samples was established for up to 77 days at −80°C.
Statistical analysis
All statistical analyses were performed using SAS statistical software version 9.4 (SAS Institute, Cary, NC), unless otherwise noted. Medical history and AEs were coded using the Medical Dictionary for Regulatory Activities version 23.0, and severity grades were assigned using the Common Terminology Criteria for Adverse Events version 5.0. Nomlabofusp plasma concentration‐time data were evaluated using summary statistics by dose group and sampling time. PK parameters were determined from the plasma concentration‐time data for nomlabofusp by noncompartmental analysis using R software version 3.6.2.
Nomlabofusp plasma concentration results below the lower limit of quantification (LLOQ) were handled as follows: (1) values after dosing and before the first value above the LLOQ were set to zero, included in noncompartmental analysis calculations, and considered missing for calculations of concentration summary statistics at nominal times; (2) values after dosing and between two values above the LLOQ were treated as missing for both noncompartmental analysis calculations and calculations of concentration summary statistics at nominal times; and (3) values after dosing and after last value above the LLOQ were set to missing for calculations of concentration summary statistics at nominal times. For the MAD study, while no individual data points were excluded from the PK noncompartmental analyses, summary statistics were not provided when >50% of the data at a specific dose and nominal time were below the LLOQ or the collection time deviated significantly from nominal (≥10% of nominal collection time and ≥1 min in the first hour, ≥10 min from hours 1–12, or ≥1 h thereafter).
In PD analyses, frataxin concentrations below the LLOQ were imputed to a value of 0.125 ng/mL (one‐half the LLOQ) and divided by the total protein in the sample. These imputed, normalized data were used in all subsequent calculations.
The geometric mean and geometric coefficient of variation were calculated for all PK parameters. Frataxin protein tissue concentrations, ratios to total protein, and change from baseline were evaluated using summary statistics.
Results
Patient disposition
In the SAD study, of the 52 patients screened for eligibility, 28 were enrolled and randomized to receive nomlabofusp (n = 18) or placebo (n = 10) (Fig. 3). The most common reasons for ineligibility to participate in the SAD study were advanced disease (e.g., unable to traverse 25 feet; n = 5), not being willing to participate in and consent to the study (n = 4), abnormal blood pressure (n = 4), and abnormal renal function (n = 3). In the MAD study, of the 36 patients screened, 27 (including 16 of 28 SAD study participants) were randomized to receive nomlabofusp (n = 20) or placebo (n = 7) (Fig. 3). Of the nine screened patients who were ineligible for the MAD study, five were excluded because of abnormal renal function, and one each was excluded due to lack of genetic FRDA confirmation, chronic cannabinoid use, withdraw of consent, and the presence of a condition, disease, or situation that the investigator judged could confound study results or put the patient at undue risk. Two patients did not complete treatment in the MAD study. One patient treated in the 25 mg cohort missed the last dose due to transport to an outside facility for the evaluation and treatment of hypertension and noncardiac chest pain, which were considered unrelated to study drug. This patient returned to the CRU to complete all study follow‐up visits. Another patient who received 50 mg of nomlabofusp discontinued the study after one dose because of mild to moderate nausea and vomiting experienced on the first day of administration.
Figure 3.
Single and multiple ascending‐dose study patient disposition. aIncludes 16 patients who completed the SAD study. Nine patients who received nomlabofusp in the SAD study were randomized to receive nomlabofusp (n = 7) and placebo (n = 2) in the MAD study. Seven patients who received placebo in the SAD study were randomized to nomlabofusp (n = 5) and placebo (n = 2) in the MAD study. bOne patient treated with nomlabofusp 25 mg missed the last dose for noncardiac chest pain and accelerated hypertension, which were considered unrelated to study drug; the patient returned to complete all study follow‐up visits. cOne patient who received nomlabofusp 50 mg discontinued due to adverse events of moderate nausea and mild vomiting. MAD, multiple ascending dose; SAD, single ascending dose.
Demographics and baseline characteristics
Baseline demographics and characteristics in both studies were as expected for adults with FRDA (Tables 1 and 2). Ages across the treatment and dose cohorts ranged from 19 to 69 years with median age at symptom onset ranging from 8 to 19 years and median age at diagnosis ranging from 13 to 28 years. All patients were homozygous for the expanded GAA triplet with the mean number of repeats ranging between 537 and 944 alleles. Most patients (>75%) relied on assistive devices for their mobility, and ~50% used a wheelchair. The median baseline mFARS_neuro score ranged between 34 and 62 across cohorts.
Table 1.
Baseline demographics and characteristics of patients in the single ascending‐dose study.
| Parameter | Placebo (n = 10) | Nomlabofusp | |||
|---|---|---|---|---|---|
| 25 mg (n = 4) | 50 mg (n = 4) | 75 mg (n = 5) | 100 mg (n = 5) | ||
| Age, years, median (range) | 31 (20–64) | 25 (20–33) | 41 (24–52) | 34 (19–69) | 24 (20–26) |
| Sex, male, n (%) | 4 (40.0) | 3 (75.0) | 4 (100) | 2 (40.0) | 4 (80.0) |
| Race, n (%) | |||||
| White | 10 (100) | 4 (100) | 4 (100) | 5 (100) | 5 (100) |
| Ethnicity, n (%) | |||||
| Not Hispanic or Latino | 8 (80.0) | 4 (100) | 4 (100) | 5 (100) | 5 (100) |
| BMI, kg/m2, mean (SD) | 23.1 (4.1) | 22.8 (4.0) | 24.2 (4.4) | 23.2 (3.9) | 26.0 (6.0) |
| Age at symptom onset, years, median (range) | 14.5 (7–40) | 8.0 (8–11) | 16.0 (10–41) | 19.0 (14–60) | 15.0 (5–18) |
| Time since diagnosis, years, median (range) | 11.4 (0.4–20.7) | 14.3 (3.8–18.7) | 13.8 (8.0–21.5) | 5.5 (2.0–12.5) | 4.8 (0.2–18.5) |
| Age at diagnosis, years, median (range) | 19.0 (8–64) | 13.0 (10–17) | 22.5 (12–44) | 28.0 (17–63) | 15.0 (5–25) |
| Assistive device, n (%) | |||||
| Wheelchair | 6 (60.0) | 3 (75.0) | 3 (75.0) | 1 (20.0) | 3 (60.0) |
| Walker | 4 (40.0) | 1 (25.0) | 0 | 1 (20.0) | 1 (20.0) |
| Cane | 0 | 0 | 0 | 2 (40.0) | 1 (20.0) |
| None | 0 | 0 | 1 (25.0) | 1 (20.0) | 0 |
| mFARS_neuro, score, median (range) | 46.5 (27–70) | 62.0 (47–67) | 52.8 (24–71) | 33.5 (27–69) | 52.5 a (13–67) |
| FARS_ADL, score, median (range) | 16.0 (10–22) | 20.8 (10–26) | 16.8 (15–25) | 16.5 (13–20) | 16.0 (8–25) |
BMI, body mass index; FARS_ADL, Friedreich's Ataxia Rating Scale‐Activities of Daily Living; mFARS_neuro, neurological scale of the modified Friedreich's Ataxia Rating Scale; SD, standard deviation.
One patient had an mFARS_neuro score that did not meet the protocol‐defined eligibility criterion of ≥20.
Table 2.
Baseline demographics and characteristics of patients in the multiple ascending‐dose study.
| Parameter | Placebo (n = 7) | Nomlabofusp | ||
|---|---|---|---|---|
| 25 mg (n = 6) | 50 mg (n = 7) | 100 mg (n = 7) | ||
| Age, years, median (range) | 23 (20–36) | 37 (21–65) | 36 (19–47) | 24 (20–44) |
| Sex, male, n (%) | 5 (71.4) | 3 (50.0) | 4 (57.1) | 3 (42.9) |
| Race, n (%) | ||||
| White | 6 (85.7) | 6 (100) | 6 (85.7) | 6 (85.7) |
| Asian | 0 | 0 | 1 (14.3) | 1 (14.3) |
| American Indian | 1 (14.3) | 0 | 0 | 0 |
| Ethnicity, n (%) | ||||
| Not Hispanic or Latino | 5 (71.4) | 6 (100) | 7 (100) | 7 (100) |
| BMI, kg/m2, mean (SD) | 24.3 (3.5) | 25.4 (3.9) | 25.2 (4.1) | 26.9 (4.7) |
| Age at symptom onset, years, median (range) | 15.0 (8–23) | 18.0 (12–44) | 19.0 (8–28) | 10.0 (5–22) |
| Time since diagnosis, years, median (range) | 5.5 (0.9–15.4) | 7.9 (0.9–19.4) | 8.6 (0.8–16.7) | 10.7 (6.8–18.8) |
| Age at diagnosis, years, median (range) | 20.0 (9–32) | 25.5 (14–64) | 28.0 (17–30) | 13.0 (5–27) |
| Assistive device use, n (%) | ||||
| Wheelchair | 4 (57.1) | 3 (50.0) | 1 (14.3) | 6 (85.7) |
| Walker | 0 | 2 (33.3) | 3 (42.9) | 0 |
| None | 2 (28.6) | 1 (16.7) | 2 (28.6) | 1 (14.3) |
| Missing | 1 (14.3) | 0 | 1 (14.3) | 0 |
| mFARS_neuro, score, median (range) | 55.0 (19–67) | 33.6 (23–65) | 33.5 (23–63) | 54.5 (43–68) |
| FARS_ADL, score, median (range) | 15.5 (10–23) | 17.3 (11–24) | 16.0 (8–24) | 17.5 (14–24) |
BMI, body mass index, FARS_ADL, Friedreich's Ataxia Rating Scale‐Activities of Daily Living; mFARS_neuro, neurological scale of the modified Friedreich's Ataxia Rating Scale; SD, standard deviation.
Safety profile
No serious AEs or deaths were reported in either study (Table 3). In the SAD study, the most common treatment‐related AEs reported in patients treated with nomlabofusp were injection site reactions (100% of patients); nausea and dizziness (17% each); and vomiting, headache, and erythema (11% each) (Table 4). One patient experienced a nonserious grade 3 (severe) event of increased hepatic enzymes that was considered to be related to the study drug. In the MAD study, the most common treatment‐related AEs reported among patients who received nomlabofusp were injection site reactions (100%), diarrhea and nausea (15% each), and headache and vomiting (10% each) (Table 4). Two patients in the MAD study experienced AEs that led to discontinuation of nomlabofusp treatment. One patient discontinued the study after the first dose because of moderate nausea and mild vomiting. The other did not receive the last dose on Day 13 as they were being evaluated off site for nonrelated, noncardiac midsternal chest pain and accelerated hypertension. However, the patient completed the study. Overall, most AEs reported in both studies were mild or moderate in severity and most resolved quickly. There were no clinically significant safety findings for vital signs, clinical laboratory tests, electrocardiogram or echocardiogram data, and no patients reported suicidal ideation in either study. The only physical examination finding considered clinically significant in either study was a small erythematous, nonraised, nontender area on the abdomen (injection site reaction) in one patient who received nomlabofusp 25 mg in the MAD study.
Table 3.
Summary of treatment‐emergent adverse events.
| Single ascending‐dose study | |||||
|---|---|---|---|---|---|
| Adverse event, n (%) | Placebo (n = 10) | Nomlabofusp | |||
| 25 mg (n = 4) | 50 mg (n = 4) | 75 mg (n = 5) | 100 mg (n = 5) | ||
| TEAE | 6 (60.0) | 4 (100) | 4 (100) | 5 (100) | 5 (100) |
| Related TEAE | 2 (20.0) | 4 (100) | 4 (100) | 5 (100) | 5 (100) |
| Serious TEAE | 0 | 0 | 0 | 0 | 0 |
| Grade ≥3 TEAE | 0 | 1 (25.0) a | 0 | 0 | 0 |
| TEAE leading to study withdrawal | 0 | 0 | 0 | 0 | 0 |
| Deaths | 0 | 0 | 0 | 0 | 0 |
| Multiple ascending‐dose study | ||||
|---|---|---|---|---|
| Adverse event, n (%) | Placebo (n = 7) | Nomlabofusp | ||
| 25 mg (n = 6) | 50 mg (n = 7) | 100 mg (n = 7) | ||
| TEAE | 7 (100) | 6 (100) | 7 (100) | 7 (100) |
| Related TEAE | 3 (42.9) | 6 (100) | 7 (100) | 7 (100) |
| Serious TEAE | 0 | 0 | 0 | 0 |
| Grade ≥3 TEAE | 0 | 1 (16.7) b | 1 (14.3) c | 0 |
| TEAE leading to study withdrawal | 0 | 1 (16.7) d | 1 (14.3) | 0 |
| Deaths | 0 | 0 | 0 | 0 |
TEAE, treatment‐emergent adverse event.
Transient grade 3 (severe) increase in associated hepatic enzymes; related to study drug per the investigator.
One grade 3 (severe) event of polycythemia; not related to study drug per investigator.
One grade 3 (severe) event of rib fracture; not related to study drug per the investigator.
One patient experienced noncardiac chest pain and accelerated hypertension and was unable to receive the final dose of study drug but completed all follow‐up visits.
Table 4.
Treatment‐related adverse events.
| Single ascending‐dose study | |||||
|---|---|---|---|---|---|
| Adverse event, n (%) | Placebo (n = 10) | Nomlabofusp | |||
| 25 mg (n = 4) | 50 mg (n = 4) | 75 mg (n = 5) | 100 mg (n = 5) | ||
| Injection site reaction | 1 (10.0) | 4 (100) | 4 (100) | 5 (100) | 5 (100) |
| Nausea | 0 | 0 | 1 (25.0) | 2 (40.0) | 0 |
| Dizziness | 0 | 0 | 0 | 3 (60.0) | 0 |
| Vomiting | 0 | 0 | 1 (25.0) | 1 (20.0) | 0 |
| Headache | 1 (10.0) | 0 | 0 | 2 (40.0) | 0 |
| Erythema | 0 | 1 (25.0) | 1 (25.0) | 0 | 0 |
| Abdominal pain | 0 | 0 | 1 (25.0) | 0 | 0 |
| Hepatic enzyme increased | 0 | 1 (25.0) | 0 | 0 | 0 |
| Presyncope | 0 | 0 | 0 | 1 (20.0) | 0 |
| Multiple ascending‐dose study | ||||
|---|---|---|---|---|
| Adverse event, n (%) | Placebo (n = 7) | Nomlabofusp | ||
| 25 mg (n = 6) | 50 mg (n = 7) | 100 mg (n = 7) | ||
| Injection site reaction | 3 (42.9) | 6 (100) | 7 (100) | 7 (100) |
| Diarrhea | 1 (14.3) | 0 | 0 | 3 (42.9) |
| Nausea | 1 (14.3) | 1 (16.7) | 1 (14.3) | 1 (14.3) |
| Headache | 0 | 0 | 2 (28.6) | 0 |
| Vomiting | 0 | 0 | 1 (14.3) | 1 (14.3) |
| Abdominal pain | 0 | 0 | 0 | 1 (14.3) |
| Dizziness | 1 (14.3) | 0 | 0 | 1 (14.3) |
| Flushing | 0 | 1 (16.7) | 0 | 0 |
| Hyperhidrosis | 0 | 0 | 0 | 1 (14.3) |
Injection site reactions reported as AEs
AEs of injection site reactions with nomlabofusp were brief, self‐limited, and mostly mild in severity. In the SAD study, the most common injection site reactions were erythema, pruritus, pain, induration, and warmth; all were mild in severity (Table 5). In the MAD study, the most common injection site reactions were erythema, pruritus, induration, and pain (Table 5). Most reactions were mild in severity; reactions resolved in a median (range) of 0.24 (0, 44.7) days.
Table 5.
Injection site reactions.
| Single ascending‐dose study | |||||
|---|---|---|---|---|---|
| Adverse event, n (%) | Placebo (n = 10) | Nomlabofusp | |||
| 25 mg (n = 4) | 50 mg (n = 4) | 75 mg (n = 5) | 100 mg (n = 5) | ||
| ≥1 injection site reaction | 1 (10.0) | 4 (100) | 4 (100) | 5 (100) | 5 (100) |
| Erythema | 0 | 4 (100) | 4 (100) | 4 (80.0) | 5 (100) |
| Pruritus | 0 | 3 (75.0) | 2 (50.0) | 4 (80.0) | 3 (60.0) |
| Pain | 1 (10.0) | 2 (50.0) | 1 (25.0) | 3 (60.0) | 2 (40.0) |
| Induration | 0 | 0 | 0 | 0 | 4 (80.0) |
| Warmth | 0 | 1 (25.0) | 3 (75.0) | 0 | 0 |
| Bruising | 0 | 0 | 0 | 0 | 2 (40.0) |
| Discomfort | 0 | 0 | 1 (25.0) | 0 | 1 (20.0) |
| Swelling | 0 | 0 | 0 | 1 (20.0) | 1 (20.0) |
| Laceration | 0 | 0 | 1 (25.0) | 0 | 0 |
| Paranesthesia | 0 | 0 | 1 (25.0) | 0 | 0 |
| Multiple ascending‐dose study | ||||
|---|---|---|---|---|
| Adverse event, n (%) | Placebo (n = 7) | Nomlabofusp | ||
| 25 mg (n = 6) | 50 mg (n = 7) | 100 mg (n = 7) | ||
| ≥1 injection site reaction | 3 (42.9) | 6 (100) | 7 (100) | 7 (100) |
| Erythema | 3 (42.9) | 6 (100) a | 7 (100) | 7 (100) |
| Pruritus | 0 | 5 (83.3) | 6 (85.7) | 7 (100) |
| Induration | 1 (14.3) | 5 (83.3) | 5 (71.4) | 7 (100) |
| Pain | 2 (28.6) | 4 (66.7) | 6 (85.7) | 6 (85.7) |
| Hemorrhage | 0 | 0 | 1 (14.3) | 4 (57.1) |
| Warmth | 0 | 2 (33.3) | 2 (28.6) | 1 (14.3) |
| Discoloration | 0 | 1 (16.7) | 0 | 0 |
| Swelling | 0 | 0 | 0 | 1 (14.3) |
One patient who received 25 mg of nomlabofusp had a finding of a small erythematous, nonraised, nontender area on the abdomen, related to study drug per the investigator.
Injection site assessments
On protocol‐specified period assessments of injection sites, findings were noted for 10 patients (56%) in the SAD study, while no findings were reported for patients who received placebo (Table S1). The most common injection site assessment finding among patients treated with nomlabofusp was tenderness (39%). In the MAD study, findings on protocol‐specified periodic assessments of injection sites were more common among patients who received nomlabofusp (90%) compared with placebo (29%). The most common injection site assessment findings among patients who received nomlabofusp were erythema (90%); other findings reported for more than half of patients were raised area (55%) and/or purpura (50%).
Pharmacokinetics
In the SAD study, samples were first analyzed using a bioanalytical assay with a higher quantifiable range (2.0–1000 ng/mL), which resulted in a higher percentage of findings below the quantifiable limit, leading to insufficient characterization. Samples from the 75 and 100 mg cohorts were reanalyzed with the 0.400–40.0 ng/mL assay as described in the Methods section. Single SC administrations of nomlabofusp were rapidly distributed in the intravascular circulation with a median t max of 0.25 h (15 min) for patients in both the 75 and 100 mg dose groups (Fig. 4 and Table 6). Following t max, a multiphasic decline was evident in both treatment groups. The geometric means for C max and AUClast were higher for the 100 mg dose compared with the 75 mg dose. The PK parameters for single 25 and 50 mg doses of nomlabofusp were not calculated because nomlabofusp plasma concentrations were generally below the limit of quantitation.
Figure 4.
Single ascending‐dose study plasma nomlabofusp concentration over time. Plasma concentrations for patients receiving 25 and 50 mg doses of nomlabofusp are not shown because concentrations were below the lower limit of quantitation.
Table 6.
Pharmacokinetic summary.
| Single ascending‐dose study | ||
|---|---|---|
| Parameter | Nomlabofusp | |
| 75 mg (n = 5) | 100 mg (n = 5) | |
| t max, h | 0.25 (0.25–0.28) | 0.25 (0.08–0.27) |
| t last, h | 4.0 (2.0–6.0) | 6.0 (6.0–12.1) |
| C max, ng/mL | 9.7 (39.5%) | 12.6 (107%) |
| AUClast, ng•h/mL | 5.6 (37.6%) | 9.6 (66.4%) |
| Multiple ascending‐dose study | |||
|---|---|---|---|
| Parameter | Nomlabofusp | ||
| 25 mg (n = 6) | 50 mg (n = 7) | 100 mg (n = 7) | |
| Day 1 | |||
| t max, h | 0.28 (0.08–0.38) | 0.25 (0.10–0.27) | 0.25 (0.08–0.50) |
| t last, h | 0.54 (0.52–2.0) | 2.0 (2.0–24.0) | 4.1 (2.0–12.1) |
| C max, ng/mL | 2.1 (72.8%) | 6.6 (44.5%) | 9.0 (66.9%) |
| AUClast, ng•h/mL | 0.90 (78.6%) | 4.6 (99.0%) | 6.7 (74.8%) |
| Day 4/7 | |||
| t max, h | 0.17 (0.08–0.33) | 0.25 (0.25–0.27) | 0.25 (0.08–0.25) |
| t last, h | 0.50 (0.50–2.1) | 3.0 (1.0–11.9) | 12.1 (6.1–24.0) |
| C max, ng/mL | 4.0 (64.0%) | 6.6 (39.1%) | 7.5 (95.9%) |
| AUClast, ng•h/mL | 1.2 (74.4%) | 3.7 (71.8%) | 14.9 (47.5%) |
| Day 13 | |||
| t max, h | 0.12 (0.08–0.32) | 0.27 (0.08–0.27) | 0.08 (0.08–0.25) |
| t last, h | 0.50 (0.45–4.1) | 4.00 (0.48–24.0) | 24.0 (12.3–24.0) |
| C max, ng/mL | 3.1 (146%) | 3.9 (62.1%) | 14.5 (156%) |
| AUClast, ng•h/mL | 1.3 (108%) | 3.5 (165%) | 30.8 (57.6%) |
Data are presented as median (range) for t max and t last and as geometric mean (geometric coefficient of variation [%]) for C max and AUClast.
AUClast, area under the plasma concentration‐time curve from time 0 to t last; C max, maximum concentration in a dosing interval; h, hour; t last, time of last quantifiable concentration in a dosing interval; t max, time of occurrence of C max.
In the MAD study, PK samples from all cohorts were analyzed with the 0.400–40.0 ng/mL assay as described in the Methods section. Two plasma samples from the 100 mg cohort that were above the upper limit of quantitation were reassessed after dilution. Peak plasma concentrations reached a maximum concentration shortly after SC administration, demonstrating the rapid uptake of nomlabofusp into the intravascular circulation (median t max, 0.08–0.28 h; Fig. 5 and Table 6). Dose‐dependent increases in nomlabofusp exposures (AUClast and C max) were observed with once‐a‐day administration for 4 days in the 25 mg cohort and 7 days in the 50 and 100 mg cohorts. Nomlabofusp exposure (AUClast) increased further through Day 13 in the 100 mg cohort, the only cohort that continued daily nomlabofusp beyond Day 7. Nomlabofusp exposures increased in a linear, dose‐proportional manner across the 25 to 100 mg range.
Figure 5.
Multiple ascending‐dose plasma nomlabofusp concentration over time on Days 1 (A), 4/7 (B), and 13 (C). Concentrations not shown for time points where >50% of the data were below the lower limit of quantitation.
Pharmacodynamics
Nomlabofusp concentrations measured using the GGM peptide were below the limit of quantitation in buccal cells, skin punch biopsies, and platelets in the MAD study. However, tissue frataxin concentrations measured with the SGT peptide were quantifiable for most samples. Tissue frataxin concentrations in buccal cells, skin punch biopsy samples, and platelets increased with increasing nomlabofusp dose and frequency in the MAD study. The median baseline buccal cell frataxin concentrations among patients receiving placebo or nomlabofusp 25 mg, 50 mg, or 100 mg were 1.99, 1.35, 2.31, and 1.83 pg/μg, respectively (Fig. 6). Median frataxin concentrations among patients receiving 50 mg or 100 mg doses of nomlabofusp were 3.89 and 4.59 pg/μg, respectively, by Day 7. The greatest dose‐dependent increases in buccal cell frataxin concentration were seen in patients who received 100 mg doses of nomlabofusp (Fig. 7A). Daily administration of 100 mg of nomlabofusp maintained buccal cell frataxin concentrations from Day 7 through Day 13. With daily administration of 50 mg of nomlabofusp, buccal cell frataxin concentrations increased; however, after administration of 50 mg of nomlabofusp was reduced to every other day after Day 7, buccal cell frataxin concentrations were lower on Day 13. The smallest changes of frataxin concentrations in buccal cells were observed for patients in the 25 mg cohort who received daily nomlabofusp doses for the first 4 days followed by one dose every third day.
Figure 6.
Multiple ascending‐dose study frataxin concentrations in buccal cells in patients receiving nomlabofusp. Frataxin concentrations measured via detection of an abbreviated n‐terminal peptide segment derived from mature frataxin. Box represents the interquartile range. Whiskers represent the minimum and maximum observed values. Dots represent individual data points. Sample collection days varied in each cohort per the trial protocol.
Figure 7.
Multiple ascending‐dose changes from baseline in frataxin concentrations in buccal cells (A), skin punch biopsy specimens (B), and platelets (C). Frataxin concentrations are measured via detection of an abbreviated n‐terminal peptide segment derived from mature frataxin. Box represents the interquartile range. Whiskers represent the minimum and maximum observed values. Dots represent individual data points. Sample collection days varied in each cohort per the trial protocol.
Twenty‐four patients participated in the optional skin biopsy evaluations before administration and on Day 13. Median baseline frataxin concentrations in skin biopsy samples among patients receiving placebo or nomlabofusp 25, 50, and 100 mg were 3.02, 1.88, 3.61, and 4.93 pg/μg, respectively. The analysis of skin biopsy specimens showed a dose‐dependent increase from baseline to Day 13 (Fig. 7B). The median baseline frataxin concentrations in platelets among patients who received placebo or nomlabofusp 25 mg, 50 mg, or 100 mg were 17.9, 19.1, 19.6, and 16.8 pg/μg, respectively. In platelets, frataxin concentrations in patients treated with 100 mg of nomlabofusp showed a distinct increase from baseline compared with placebo and other nomlabofusp doses. There were no changes from baseline in platelet frataxin concentrations for lower doses of nomlabofusp (Fig. 7C).
Discussion
Currently, there are no treatment options that address the low concentrations of frataxin, the underlying etiology of FRDA. Nomlabofusp, a recombinant fusion protein, is being developed as a novel, specific treatment to supplement frataxin concentrations in the mitochondria of adults and children with FRDA and is the first potential therapy designed to address the core mitochondrial deficiency of the disease by delivering frataxin.
Single and multiple doses of nomlabofusp up to 100 mg administered SC for up to 13 days were well tolerated. No serious AEs or deaths were reported. Most AEs were mild or moderate in severity. The most frequently reported treatment‐related AEs among patients receiving nomlabofusp (reported for >15% of patients in either study) were injection site reactions, nausea, dizziness, and diarrhea. Injection site reactions are common with SC administrations. All patients receiving nomlabofusp reported an injection site reaction; all were mild in severity in the SAD study and the majority were mild in severity in the MAD study. Injection site reactions with nomlabofusp occurred on the day of administration and were transient. In comparison, 10.0% and 42.9% of patients receiving placebo reported an injection site reaction in the SAD and MAD studies, respectively.
One patient discontinued the MAD study after the first dose for transient mild vomiting and moderate nausea. Another patient did not receive the last dose on Day 13 because of a nonstudy related AE. The patient continued to the end of the study.
The achievement of peak plasma concentrations of nomlabofusp at around 15 min after SC administration demonstrates that nomlabofusp is rapidly absorbed into the intravascular circulation. The subsequent rapid decline in plasma concentrations of nomlabofusp may reflect tissue and, potentially, intracellular uptake of nomlabofusp, but may also be partially due to proteolysis of nomlabofusp. Daily administration generally resulted in increased nomlabofusp exposure over time and decreased with less‐frequent administration, suggesting that a longer period of daily administration may be required to maintain exposure.
Given that nomlabofusp tissue concentrations measured using the GGM peptide (which is unique to nomlabofusp and not present in mature human frataxin) were undetectable, the tissue frataxin concentrations detected using the SGT peptide are considered to be mature human frataxin. Frataxin concentrations in buccal cells, skin tissue, and platelets increase with increasing nomlabofusp administration, which is consistent with nomlabofusp exiting the general circulation, penetrating cells, and increasing tissue frataxin concentrations. The higher frataxin concentrations observed on Day 7 after daily administration of 50 and 100 mg doses of nomlabofusp indicate potentially meaningful increases in tissue frataxin concentrations in patients with FRDA. Because 25 mg doses were only administered daily for 4 days then every third day, it is not known if potentially meaningful increases would have been achieved with more frequent or longer administration of nomlabofusp at that dose. A prior study evaluating the relationship between tissue frataxin concentrations and progression of FRDA reported that patients with FRDA who had incrementally higher tissue frataxin concentrations reported a later onset of disease and a lower rate of increase in the annual FRDA rating scale. 6 These data suggest the incremental increases in tissue frataxin concentrations observed after 7 and 13 days of nomlabofusp administration may slow disease progression.
Limitations of this study include the relatively short duration of treatment (a maximum of 13 days) and the small patient populations assessed. Relevant changes in clinical parameters were not expected given the short duration of treatment and relatively slow progression of the disease.
Results from the safety and tolerability assessments in both studies support a favorable safety profile for nomlabofusp in the treatment of patients with FRDA. Increases in frataxin concentrations in the tissues studied are encouraging and warrant the continued evaluation of treatment beyond 13 days. These data demonstrate that SC administration is an effective route to deliver nomlabofusp in patients. Analysis of the PK and PD profiles of patient cohorts that received nomlabofusp support using a cell‐penetrant, peptide‐mediated frataxin delivery to supplement low concentrations of frataxin in patients with FRDA.
Future studies will evaluate long‐term safety and efficacy of nomlabofusp. Thus far, nomlabofusp studies have included patients ≥18 years old. Since symptoms of FRDA typically appear in childhood or early adolescence, 2 the safety, tolerability, and efficacy of nomlabofusp should be assessed in younger patients.
Author Contributions
R.C., T.G., N.S., J.F., and N.R. contributed to the conception and design of the study. D.S. and D.B. contributed to data acquisition. M.H. contributed to statistical analysis. R.C., T.G., N.S., J.F., N.R., M.H., D.S., and D.B. contributed to data interpretation. All authors critically reviewed and approved the manuscript for submission.
Conflict of Interest
R.C. is a former consultant for and current employee of Larimar Therapeutics, Inc. and may hold Larimar stock or stock options. J.F. is employed by the Friedreich's Ataxia Research Alliance. T.G., N.S., and M.H. are current employees of Larimar Therapeutics, Inc. and may hold Larimar stock or stock options. N.R., D.S., and D.B are former employees of Larimar Therapeutics, Inc. and may hold Larimar stock or stock options.
Supporting information
Table S1. Periodic injection site assessment findings.
Acknowledgements
Larimar Therapeutics, Inc., participated in the study design; study research; collection, analysis, and interpretation of data; writing, reviewing, and approving this manuscript in its entirety. All authors had access to the data; participated in the development, review, and approval of the manuscript; and agreed to submit this manuscript for publication. Larimar and the authors thank all study investigators for their contributions and the patients who participated in these studies. The authors acknowledge Magdy L. Shenouda, MD (Clinilabs, Inc., New York, NY), for his role as principal investigator; Angela Miller, MS (formerly of Larimar Therapeutics, Inc.), for her contribution to data collection; Jeannine Fisher, MS (Metrum Research Group), and C. J. Godfrey, PhD (Metrum Research Group), for their contribution to data analysis; David R. Lynch, MD, PhD (Children's Hospital of Philadelphia), for his contributions to the concept/design of the study, data interpretation, and review of the manuscript. Larimar funded the research for these studies and provided writing support for this manuscript. Medical writing assistance, funded by Larimar, was provided by Nancy Niguidula, DPH, and Lisa M. Pitchford, PhD, ISMPP CMPP™, of JB Ashtin. No honoraria or payments were made for authorship.
Funding Information
Larimar Therapeutics.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Table S1. Periodic injection site assessment findings.