2025 Volume 72 Issue 8 Pages 897-909
This phase 1 dose-escalation study evaluated the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of K1-70TM, a TSH-receptor-specific monoclonal autoantibody that inhibits ligand binding and receptor activation, in Japanese Graves’ disease (GD) patients. Twelve patients were enrolled, divided into four dosage cohorts (5 mg, 25 mg, 75 mg, and 150 mg), and monitored for 100 days post-administration. The primary objective was to assess safety and tolerability, and the secondary objectives were evaluation of PK and thyroid function. Exploratory analyses focused on the dynamics of the anti-TSH receptor antibodies and Thyroid eye disease (TED). K1-70TM demonstrated a favorable safety profile, with no reports of serious adverse events. Mild to moderate treatment-emergent adverse events, such as headache and fatigue, were observed in 83.3% of the participants, but none were deemed severe. PK analysis revealed a dose-dependent increase in half-life, suggesting prolonged systemic exposure at higher doses. Thyroid function remained stable at lower doses, but there were dose-dependent reductions at higher doses that were managed with adjunctive L-thyroxine therapy. Marked reductions in TSAb levels were observed across all cohorts, indicating effective suppression of TSH receptor activity. An improvement in proptosis was noted in 50% of the eyes, suggesting a potential therapeutic benefit against inactive-phase TED. These findings support K1-70TM as a promising targeted therapy for GD and TED, and they warrant further studies involving larger patient populations and active disease phases to confirm its efficacy and safety (jRCT Registration Number: JRCT2080224902).
Graves’ disease (GD) is an autoimmune disorder triggered by autoantibodies that target the thyroid-stimulating hormone receptor (TSH receptor), primarily resulting in hyperthyroidism [1]. GD is frequently manifested by ophthalmic symptoms such as exophthalmos, eyelid edema, and visual impairments, commonly referred to as Thyroid eye disease (TED), which sometimes progress to severe stages. These symptoms significantly impair patients’ quality of life and necessitate timely and effective therapeutic interventions. According to 2020 data from Japan, out of 2,613 patients with severe TED, 325 individuals (12.4%) required systemic glucocorticoid therapy or ophthalmic surgery within two years post-diagnosis, while 82 patients (3.1%) developed the most severe manifestations, such as optic neuritis and optic neuropathy [2]. Although systemic glucocorticoid therapy and surgical interventions [3] have long been used to treat severe cases, relapse and adverse effects have persisted as major challenges.
In some countries, other drugs, including anti-IL-6 receptor monoclonal antibodies (e.g., tocilizumab), anti-CD20 monoclonal antibodies (e.g., rituximab), and TNF-α-blocking monoclonal antibodies (e.g., adalimumab), have recently become available for the treatment of TED [4], but their potent immunosuppressive actions entail a significant risk of severe adverse effects, including increased susceptibility to infections.
One of the suspected pathophysiological mechanisms responsible for TED involves thyroid-stimulating antibody (TSAb), which targets TSH receptors on orbital fibroblasts [5, 6]. Because of the possible interaction, or “cross-talk,” between TSH receptors and IGF-1 receptors, interest has recently centered on the anti-IGF-1 receptor monoclonal antibody Teprotumumab as a potential therapeutic option [7].
In this trial we investigated K1-70TM, an inhibitory human monoclonal antibody that targets the TSH receptor [8, 9] and is expected to directly inhibit TSAb action [10]. Unlike conventional therapies, K1-70TM may address the underlying causes of both GD and TED, thereby potentially avoiding the adverse effects associated with immunosuppressive approaches. This Phase 1 trial was designed to evaluate the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of K1-70TM in Japanese GD patients. The results of this study may contribute to expanding the treatment options for GD and TED, thereby representing a crucial step toward establishing novel therapeutic approaches grounded in immunological advancements.
Recombinant human K1-70TM immunoglobulin G (IgG) was produced in CHO cells based on current good manufacturing practice and formulated at 10 mg/mL in 25 mmol/L sodium citrate; 75 mmol/L sodium chloride; 50 mmol/L glycine; 0.02% (wt/vol) polysorbate 80; pH 6.0, and it was designated for intravenous (IV) administration.
Trial objectives Primary objectiveTo evaluate the safety and tolerability of a single intravenous infusion of K1-70TM in GD patients.
Secondary objectivesTo assess the pharmacokinetics of a single intravenous infusion of K1-70TM in GD patients.
To evaluate the immunogenicity of K1-70TM in GD patients.
To assess the effect of a single intravenous infusion of K1-70TM on thyroid function in GD patients.
Exploratory objectivesTo investigate the correlation between baseline concentrations of anti-TSH receptor antibodies (TRAbs), including thyroid-stimulating antibodies (TSAb) and thyroid-stimulation-blocking antibodies (TSBAb), and the levels of pharmacodynamic markers, and to explore the effects of K1-70TM on TED.
Study design and recruitmentThis Phase 1 clinical trial was conducted in accordance with the ethical principles of the Declaration of Helsinki, the Pharmaceuticals and Medical Devices Act, and the “Ministerial Ordinance on Good Clinical Practice” as established by the Minister of Health, and in strict compliance with the trial protocol. It was approved by the Ethics Committee of National Hospital Organization Kyoto Medical Center (Approval No.: NSY-K1-70-IV-101) and Ito Hospital (Approval No.: 311) and has been registered with the Japan Registry of Clinical Trials (jRCT) under registration number JRCT2080224902.
All participants were fully informed about the investigational drug, the purpose and design of the study, and the potential risks, and written informed consent was obtained from each participant.
GD patients between 20 years of age and 73 years of age, irrespective of gender, who had a body mass index between 18.5 kg/m2 and 35.0 kg/m2 at screening, were eligible to participate in the study. Pregnant patients were excluded. Eligible patients included patients who had been on a stable dose of antithyroid medication for at least six weeks prior to consent, patients whose thyroid function was clinically and biochemically normal or who were hyperthyroid both when screened and on Day –1, and patients who had been off antithyroid medication for at least six weeks due to intolerance but who were clinically and biochemically hyperthyroid both when screened and on Day –1. GD patients with TED who had a clinical activity score (CAS) [11] greater than 3 out of 7 or evidence of optic neuropathy and/or corneal destruction at screening, were excluded because of the potential, albeit low, risk of unexpected worsening of TED after K1-70TM administration.
The subjects were divided into four cohorts of three subjects each, and there was the option of adding an additional three subjects to each cohort, if necessary, resulting in a planned minimum of 12 subjects and maximum of 24 subjects. The protocol included provisions for enrolling additional subjects in case of serious adverse events (SAEs) or for other safety concerns. However, since no SAEs or safety concerns arose, the trial was successfully completed with 12 subjects.
K1-70TM is in the early stages of clinical development. Since it was administered to Japanese patients for the first time in this trial, a sequential cohort dose-escalation design was chosen for safety reasons. In a Phase 1 trial of K1-70TM conducted in the United Kingdom (UK) [12], a 50 mg intravenous infusion was administered, and the Safety Review Committee (SRC) concluded that the dose was safe and well-tolerated. Based on these findings, the initial cohort dose in Japan was set at a newly established level of 5.0 mg, i.e., at one-tenth the dose used in the UK trial.
In the first cohort, a sentinel subject was administered the 5.0 mg dose and then observed for 13 days. Since the safety and tolerability profile was deemed acceptable, K1-70TM was then administered to the remaining two subjects at the same dose. The subsequent dose-escalation cohorts were subjected to the same procedure to ensure prevention of serious adverse events in each cohort.
Whether to continue dosing in the remaining subjects was decided by the principal investigator.
If no clinically significant changes in the thyroid function test (TFT) were observed after dosing, dose escalation of up to 5 fold was allowed. Clinically significant changes in the TFT were defined as a change of more than 50% in both FT4 and TSH values compared to their pre-dose levels (Day 1), with the FT4 level falling below the lower limit of the normal range and the TSH level exceeding the upper limit of the normal range and both values failing to return to normal within 7 days. If at least one subject in each cohort exhibited a clinically significant changes in the TFT, the SRC reconsidered the multiple of the dose escalation. If clinically meaningful pharmacological effects, indicated by significant changes in the TFT, were observed and the TFT values did not return to normal, the dose escalation in the next cohort was limited to a maximum of twofold.
Dosing in subsequent cohorts was determined based on a review of the cumulative safety, tolerability, pharmacokinetic, and pharmacodynamic data from the preceding cohort.
Subjects were followed up after dosing, as shown in Fig. 1. A comprehensive assessment of safety and tolerability was conducted at entry and throughout the follow-up period, including an injection site evaluation, vital signs, physical examination, electrocardiogram, clinical laboratory tests (serum biochemistry, hematology, coagulation tests, urinalysis, serology, FT3, FT4, TSH), TRAb (TSAb, TSBAb), anti-drug antibodies (ADA), pregnancy tests, and ophthalmologic examinations.
Screening period (Day –28 to Day –3)
Hospitalization (Day –1 to Day 3). Single dose of K1-70TM on Day 1
96-day follow-up period (Day 4 to Day 100)
Complete eye examinations (including CAS) were performed by appropriately qualified members of the ophthalmology team at screening and on Days 14, 42, 70, and 100. Abbreviated eye examinations were conducted by the study physician on Days 1, 3, 7, 14, 21, 28, 42, 56, 70, and 100. A Hertel exophthalmometer was used to measure the degree of proptosis. Eye examinations were carried out in accordance with the recommendations of the European Group on Graves’ Orbitopathy (EUGOGO) guidelines for the management of Graves’ Orbitopathy.
All observations, examinations, and safety assessments, including the results for pharmacodynamic (PD) markers, pharmacokinetics (PK), and ADA, as well as concomitant medications and treatment-emergent adverse events (TEAEs), were documented using an electronic case report form. Serum concentrations of K1-70TM were measured by BML, Inc. (Tokyo, Japan), using the enzyme-linked immunosorbent assay (ELISA) kit provided by RSR Ltd (Cardiff, UK). Specific antibodies against K1-70TM IgG generated in response to K1-70TM administration were detected using an ADA assay developed specifically with the Meso Scale Discovery’s electrochemiluminescence detection platform.
Study subjects and dosing regimenIn the 5 mg cohort (Cohort 1), based on the Day 1 baseline values both the TSH and FT4 levels remained within acceptable ranges during the 100-day post-administration observation period. More specifically, the TSH level never increased 1.5-fold over its baseline value, and the FT4 level never fell below 50% of its baseline value during the observation period. It was therefore determined in accordance with the escalation protocol that the dose could be increased by a factor of five, i.e., to 25 mg, in Cohort 2.
Similarly, in the 25 mg cohort (Cohort 2), both the TSH and FT4 levels met the same criteria throughout the 100-day observation period, thereby allowing a further three-fold escalation to 75 mg in Cohort 3. However, in the 75 mg cohort (Cohort 3), the TSH levels exceeded a 1.5-fold increase from baseline and the FT4 levels dropped below 50% of baseline and below the lower limit of the normal range. In addition, the TSH levels rose above the upper limit of the normal range, and both the FT4 and TSH levels failed to return to normal within seven days. Consequently, the dose escalation for Cohort 4 was adjusted to a two-fold increase to 150 mg.
Fifteen GD subjects were screened, and the 12 who met the eligibility criteria were enrolled in the study. All 12 subjects received K1-70TM and completed the 100-day follow-up period. The subjects were randomly assigned to one of the four dosage cohorts: Cohort 1 (5 mg), Cohort 2 (25 mg), Cohort 3 (75 mg), and Cohort 4 (150 mg).
The demographic data of the subjects are shown in Table 1. Among the 12 patients evaluated, the median duration of Graves’ disease was 48.5 months (range, 16–384 months), while the median duration of ophthalmopathy was 19.5 months (range, 0–384 months). The baseline CAS values of the participants ranged from 0 to 1 out of a possible maximum of 7, and the baseline exophthalmometry measurements ranged from 13 mm to 24 mm. The baseline TFT parameters are also shown in Table 1. Prior to K1-70TM administration, nine of the 12 participants were TRAb-positive, and three were TRAb-negative (defined as <2.0 IU/L). Importantly, their TRAb status did not impact eligibility, cohort assignment, or dose-escalation decisions.
| Variable | Value |
|---|---|
| Female vs. Male, n (%) | 11 (92), 1 (8) |
| Age (years), mean (±2SD) | 45 (20–69) |
| BMI (kg/m2), median (range) | 22.5 (18.9–28.1) |
| TSH (μIU/mL), median (range), reference range: 0.5–5.0 |
0.8 (0.005–3.6) |
| FT3 (pg/mL), median (range), reference range: 2.3–4.0 |
3.2 (2.6–10.7) |
| FT4 (ng/dL), median (range), reference range: 0.9–1.7 |
1.2 (0.6–4.1) |
| TRAb (IU/mL), positive ≥2.0 | 7.5 (1.2–40.0) |
| Patients taking ATDs | |
| Methimazole, n (%) | 12 (100) |
| Inorganic iodine, n (%) | 3 (25) |
| Clinical Status | |
| Euthyroid on ATD, n (%) | 8 (66.6) |
| Latent hyperthyroid, n (%) | 2 (16.7) |
| Hyperthyroid, n (%) | 2 (16.7) |
TSH, serum-free triiodothyronine (FT3), and serum-free thyroxine (FT4) were measured using electrochemiluminescence immunoassay kits, i.e., with ECLusys TSH, ECLusys FT3, and ECLusys FT4, respectively (Roche Diagnostics, Basel, Switzerland), and the reference ranges provided by the manufacturer were: TSH 0.5–5.0 μIU/mL, FT3 2.3–4.0 pg/mL, and FT4 0.9–1.7 ng/dL, respectively. TRAb was measured using an ECLusys TRAb electrochemiluminescence immunoassay kit (normal range, <2.0 IU/L; Roche Diagnostics). TSAb and TSBAb were measured using a TSAb enzyme immunoassay (EIA) and TSBAb EIA (Yamasa, Choshi, Japan), and the cutoff values were set at <120% and <34%, respectively.
Statistical analysisThe data are reported as the mean and standard deviation (SD) for normal distributions, and as the median and range for non-normal distributions. The changes in proptosis after K1-70TM administration were statistically analyzed using the sign test. We regarded results with a p-value below 0.05 as statistically significant. All our statistical evaluations were performed using the JMP v18.1 software program.
K1-70TM was safe and well-tolerated at all doses and in all subjects. A total of 12 TEAEs were observed in 10 subjects (83.3%), all of which were non-serious (Table 2). In Cohort 1, 3 TEAEs were reported; in Cohort 2, 6; and in Cohorts 3 and 4, 8 each. TEAEs observed in more than 10% (2) of the subjects consisted of only headache, epistaxis, and fatigue, each in 16.7% (2/12 cases). The severity of the TEAEs was mild, except for one case of moderate fever in Cohort 3 and one case of moderate headache in Cohort 4. No SAE, no deaths, and no adverse events that led to discontinuation were observed. None of the TEAEs was deemed directly related to K1-70TM itself.
| Cohort 1 (5 mg, n = 3) |
Cohort 2 (25 mg, n = 3) |
Cohort 3 (75 mg, n = 3) |
Cohort 4 (150 mg, n = 3) |
|
|---|---|---|---|---|
| Number of cases with a TEAE | 3 (100%) | 2 (67%) | 2 (67%) | 3 (100%) |
| Total number of TEAEs | 3 | 6 | 8 | 8 |
| Total with a serious TEAE | 0 | 0 | 0 | 0 |
| Relationship of TEAEs to study treatmenta | ||||
| Not related b | 3 | 6 | 7 | 7 |
| Possibly Related c | 0 | 0 | 1 | 1 |
| Related | 0 | 0 | 0 | 0 |
| Severity of TEAEs | ||||
| Mild | 3 | 6 | 7 | 7 |
| Moderate | 0 | 0 | 1 | 1 |
| Severe | 0 | 0 | 0 | 0 |
| Types of adverse events | Headache, dry eye, punctate keratitis | Headache, dizziness, epistaxis, muscle pain, nausea, injection site reaction, muscle detachment | Headache, eye discomfort, back pain, attention disorder, nausea, fatigue, fever | Adaptive disorder, headache, epistaxis, dizziness, joint pain, muscle pain, fever |
aIf a subject experienced more than one TEAE, the subject was counted only once, based on the most severe or most related event.
bNot related TEAEs refer to the total number of TEAEs classified as not related or unlikely related to the study drug.
cPossibly related TEAEs are those classified as possibly related to the study drug (no TEAEs were classified as definitively related to the study drug).
The serum concentrations of K1-70TM following administration are shown in Fig. 2. The median half-life of K1-70TM increased with the dose up to the 75 mg dose. The median half-life was 281 hours (11.7 days) after the 5.0 mg dose, 318 hours (13.3 days) after the 25 mg dose, 498 hours (20.8 days) after the 75 mg dose, and 469 hours (19.5 days) after the 150 mg dose. The slight decrease in half-life at 150 mg may have been attributable to saturation of the elimination pathways or to inter-individual variability. Further studies will be required to confirm this trend. The median times to the maximum observed serum concentration (Tmax) following the K1-70TM doses of 5.0 mg, 25 mg, 75 mg, and 150 mg were 40 min, 80 min, 98 min, and 150 min, respectively.
Vertical bars indicate the range. The times shown were measured from the end of the IV infusion.
ADA testing was negative in all subjects except one subject in Cohort 1 and one subject in Cohort 3, and both positive tests were attributed to pre-existing cross-reactivity, confirmed by additional assays. In the Cohort 1 subject, ADA testing was already positive before administration on Day 1, and the subject had a weakly positive titer of 10- to 20-fold from pre-administration through Day 100. In the Cohort 3 subject, the ADA titers were 10- to 20-fold on Days 7, 14, and 21, but became negative by the final evaluation on Day 100.
Pharmacodynamic effects on GD Post-K1-70TM dynamics of FT3, FT4, and TSHBefore K1-70TM administration, GD was controlled with methimazole (MMI) or a combination of MMI and inorganic iodine (Inorg I). After K1-70TM administration and the subsequent TSH elevation, control was achieved through a reduction in MMI and Inorg I and the addition of L-thyroxine. The thyroid function testing on Day 1 prior to K1-70TM administration revealed one case of latent hyperthyroidism and two cases of overt hyperthyroidism in Cohort 2, and one case of latent hyperthyroidism each in Cohort 3 and Cohort 4 (Table 3). All three cases in Cohort 1 were controlled on MMI. Case 2 exhibited latent hypothyroidism from Day 21 to Day 56, but thyroid function remained normal in the other cases. In Cohort 2, Case 4 and Case 5 were controlled with a combination of MMI and Inorg I, while Case 6 was managed with MMI alone. Case 4 experienced mild hyperthyroidism that persisted until Day 28, and in Case 5, it continued until Day 100. Case 6 remained in a state of latent to mild hyperthyroidism throughout the observation period.
| Cohort Number (dose) |
Case Number | Variable (units) | Day 1 | Day 2 | Day 3 | Day 4 | Day 7 | Day 14 | Day 21 | Day 28 | Day 42 | Day 56 | Day 70 | Day 100 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cohort 1 (5 mg) | 1 | TSH (μIU/mL) | 2.53 | 2.75 | 2.45 | 3.09 | 3.62 | 2.39 | 3.21 | 1.84 | 1.58 | 1.50 | 2.59 | 1.05 |
| FT4 (ng/dL) | 1.30 | 1.37 | 1.23 | 1.33 | 1.30 | 1.36 | 1.53 | 1.42 | 1.42 | 1.44 | 1.54 | 1.35 | ||
| FT3 (pg/mL) | 2.57 | 2.98 | 2.89 | 2.89 | 2.66 | 3.07 | 3.55 | 2.92 | 2.86 | 3.44 | 3.39 | 2.87 | ||
| 2 | TSH (μIU/mL) | 2.23 | 2.49 | 2.71 | 2.79 | 4.82 | 3.67 | 5.56 | 6.10 | 6.95 | 7.99 | 2.99 | 4.63 | |
| FT4 (ng/dL) | 1.22 | 1.09 | 1.13 | 1.03 | 1.02 | 1.16 | 1.21 | 1.07 | 1.15 | 1.07 | 1.10 | 1.33 | ||
| FT3 (pg/mL) | 3.21 | 2.69 | 2.65 | 2.65 | 2.60 | 2.74 | 3.12 | 2.46 | 2.67 | 2.54 | 2.82 | 3.04 | ||
| 3 | TSH (μIU/mL) | 0.79 | 0.71 | 1.00 | 1.11 | 1.68 | 0.92 | 1.19 | 0.68 | 0.69 | 0.53 | 0.50 | 0.38 | |
| FT4 (ng/dL) | 1.08 | 1.09 | 1.16 | 1.12 | 1.22 | 1.11 | 0.97 | 1.15 | 1.12 | 1.14 | 1.19 | 1.23 | ||
| FT3 (pg/mL) | 2.84 | 2.63 | 2.99 | 2.79 | 3.30 | 2.94 | 2.85 | 3.25 | 3.15 | 3.02 | 3.40 | 3.29 | ||
| Cohort 2 (25 mg) | 4 | TSH (μIU/mL) | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | 0.01 | 0.06 |
| FT4 (ng/dL) | 1.48 | 1.38 | 1.43 | 1.49 | 1.32 | 1.35 | 1.36 | 1.28 | 1.13 | 0.81 | 0.78 | 0.71 | ||
| FT3 (pg/mL) | 4.98 | 4.73 | 4.16 | 4.16 | 3.72 | 3.83 | 4.24 | 4.28 | 3.26 | 2.44 | 2.50 | 2.30 | ||
| 5 | TSH (μIU/mL) | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | <0.005 | |
| FT4 (ng/dL) | 3.59 | 3.41 | 3.45 | 3.34 | 3.40 | 3.30 | 2.81 | 2.66 | 2.89 | 3.00 | 2.42 | 2.31 | ||
| FT3 (pg/mL) | 9.15 | 8.62 | 7.93 | 6.49 | 7.47 | 7.32 | 7.12 | 6.08 | 6.63 | 6.95 | 5.32 | 5.17 | ||
| 6 | TSH (μIU/mL) | <0.005 | <0.005 | <0.005 | <0.005 | 0.01 | 0.04 | 0.01 | <0.005 | <0.005 | <0.005 | 0.01 | 0.01 | |
| FT4 (ng/dL) | 1.44 | 1.46 | 1.30 | 1.32 | 1.16 | 1.17 | 1.55 | 1.78 | 1.65 | 1.65 | 1.54 | 1.35 | ||
| FT3 (pg/mL) | 3.76 | 3.88 | 3.21 | 3.19 | 2.69 | 3.38 | 4.05 | 4.74 | 4.73 | 4.21 | 4.28 | 3.61 | ||
| Cohort 3 (75 mg) | 7 | TSH (μIU/mL) | 0.95 | 0.80 | 1.58 | 3.00 | 6.51 | 23.00 | 32.20 | 30.80 | 0.34 | 0.06 | 0.24 | 2.01 |
| FT4 (ng/dL) | 0.96 | 1.07 | 0.95 | 0.85 | 0.67 | 0.41 | 0.66 | 0.73 | 2.09 | 2.25 | 1.36 | 1.25 | ||
| FT3 (pg/mL) | 2.32 | 2.23 | 2.15 | 2.16 | 1.64 | 1.27 | 1.92 | 1.74 | 3.61 | 3.91 | 2.68 | 2.84 | ||
| 8 | TSH (μIU/mL) | 0.75 | 0.55 | 0.60 | 0.97 | 1.95 | 3.79 | 1.17 | 0.92 | 0.55 | 2.05 | 1.52 | 0.73 | |
| FT4 (ng/dL) | 1.36 | 1.43 | 1.54 | 1.22 | 1.19 | 1.02 | 1.24 | 1.24 | 1.36 | 1.32 | 1.32 | 1.46 | ||
| FT3 (pg/mL) | 2.55 | 2.56 | 2.36 | 2.59 | 2.01 | 2.04 | 2.52 | 2.72 | 2.55 | 2.54 | 2.75 | 2.53 | ||
| 9 | TSH (μIU/mL) | 0.01 | 0.01 | 0.01 | 0.01 | 0.02 | 2.20 | 7.79 | 3.26 | 0.14 | 0.01 | <0.005 | <0.005 | |
| FT4 (ng/dL) | 0.51 | 0.47 | 0.50 | 0.50 | 0.42 | 0.18 | 0.45 | 0.52 | 0.69 | 6.09 | 4.39 | 5.36 | ||
| FT3 (pg/mL) | 3.13 | 2.58 | 2.11 | 1.64 | 0.58 | 0.80 | 1.26 | 2.58 | 2.68 | 13.20 | 12.30 | 16.90 | ||
| Cohort 4 (150 mg) | 10 | TSH (μIU/mL) | 0.83 | 0.48 | 0.40 | 1.12 | 2.63 | 12.40 | 34.50 | 56.80 | 27.90 | 13.00 | 0.50 | 0.03 |
| FT4 (ng/dL) | 1.36 | 1.54 | 1.49 | 1.31 | 1.06 | 0.83 | 0.71 | 0.64 | 0.94 | 1.33 | 1.84 | 2.17 | ||
| FT3 (pg/mL) | 2.94 | 3.12 | 2.52 | 2.46 | 2.16 | 2.09 | 1.84 | 1.42 | 2.68 | 2.97 | 3.69 | 4.63 | ||
| 11 | TSH (μIU/mL) | 0.57 | 0.68 | 1.26 | 4.07 | 7.54 | 18.60 | 21.30 | 17.60 | 14.20 | 5.64 | 2.26 | 1.97 | |
| FT4 (ng/dL) | 1.08 | 1.00 | 0.94 | 0.90 | 0.68 | 0.43 | 0.33 | 0.65 | 1.00 | 1.18 | 1.35 | 1.39 | ||
| FT3 (pg/mL) | 2.69 | 2.30 | 2.16 | 1.92 | 1.54 | 1.22 | 0.73 | 1.27 | 1.79 | 2.14 | 2.68 | 2.61 | ||
| 12 | TSH (μIU/mL) | <0.005 | <0.005 | <0.005 | <0.005 | 0.06 | 2.58 | 12.60 | 18.90 | 11.10 | 0.67 | 0.06 | 0.03 | |
| FT4 (ng/dL) | 1.45 | 1.40 | 1.45 | 1.36 | 0.93 | 0.48 | 0.56 | 0.62 | 0.86 | 1.21 | 1.28 | 1.23 | ||
| FT3 (pg/mL) | 3.27 | 3.37 | 2.74 | 2.49 | 1.65 | 1.01 | 0.96 | 1.45 | 1.76 | 2.53 | 3.06 | 2.62 |
On Day 1, FT3, FT4, and TSH samples were obtained prior to the administration of K1-70TM.
In Cohort 3, Case 7 and Case 8 were controlled with MMI, while Case 9 was managed with MMI and Inorg I. In Case 7, the TSH level rose from 6.51 to 23.0, 32.2, and 30.8 μIU/mL between Day 7 and Day 28, and the FT3 level decreased to 2.23 on Day 2 and remained below the normal range until Day 28. In Case 9, the FT3 level began to decrease on Day 2 and fell below the normal range by Day 3, but by Day 56 the FT4 and FT3 levels had surged to 6.09 and 13.2, respectively, resulting in thyrotoxicosis. Case 9 was managed with MMI 20 mg and Inorg 38 mg, but due to rapid decreases in FT3 and FT4, the patient was treated with L-thyroxine 50 μg from Day 16 to Day 39. However, the patient subsequently developed thyrotoxicosis by Day 56. In Cohort 4, the FT3 level decreased below the normal range from Day 3 to Day 7, and the TSH level increased on Days 7, 14, and 21; the decrease in FT3 preceded the increase in TSH in every case. In Cohort 4, L-thyroxine was added as the FT3 level decreased, and the MMI dose was subsequently reduced.
Post-K1-70TM dynamics of TRAb, TSAb, and TSBAb TRAbIn Cohort 1, all three cases had TRAb levels that exceeded the upper limit of detection on Day 7, but they returned to baseline by Day 100 (Table 4). In Cohort 2, the TRAb levels of the three subjects remained above the upper limit until Day 28, Day 42, and Day 70, respectively, and elevated levels were still present in two cases at Day 100. In five of the six cases in Cohorts 3 and 4, the TRAb levels exceeded the upper limit of detection from Day 7 to Day 100.
| Cohort Number (dose) |
Case Number | Variable (units) |
Day 1 | Day 7 | Day 14 | Day 21 | Day 28 | Day 42 | Day 56 | Day 70 | Day 100 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Cohort 1 (5 mg) |
1 | TRAB (IU/L) | 2.5 | ≥40.1 | 39.5 | 35.9 | 33.0 | 24.5 | 17.5 | 12.6 | 5.5 |
| TSAb (%) | 155 | 125 | 141 | 160 | 120 | 132 | 139 | 132 | 121 | ||
| TSBAb (%) | 0 | 98 | 0 | ||||||||
| 2 | TRAB (IU/L) | 7.3 | ≥40.1 | 36.4 | 33.0 | 27.8 | 19.4 | 13.1 | 9.3 | 6.5 | |
| TSAb (%) | 803 | 134 | 106 | 140 | 125 | 180 | 181 | 418 | 732 | ||
| TSBAb (%) | 0 | 99 | 0 | ||||||||
| 3 | TRAB (IU/L) | 1.2 | ≥40.1 | 33.9 | 30.2 | 24.2 | 9.5 | 7.2 | 1.9 | 1.1 | |
| TSAb (%) | 144 | 146 | 142 | 127 | 112 | 117 | 141 | 114 | 131 | ||
| TSBAb (%) | 0 | 96 | 0 | ||||||||
| Cohort 2 (25 mg) |
4 | TRAB (IU/L) | 32.8 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | 30.0 |
| TSAb (%) | 6,006 | 135 | 151 | 128 | 163 | 149 | 153 | 168 | 285 | ||
| TSBAb (%) | 100 | 91 | |||||||||
| 5 | TRAB (IU/L) | 6.8 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | 32.7 | 25.4 | 13.2 | 7.1 | |
| TSAb (%) | 126 | 110 | 102 | 103 | 116 | 124 | 109 | 100 | 127 | ||
| TSBAb (%) | 0 | 99 | 0 | ||||||||
| 6 | TRAB (IU/L) | 17.7 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | 38.5 | 33.0 | 24.9 | |
| TSAb (%) | 1,250 | 123 | 121 | 122 | 136 | 124 | 155 | 123 | 151 | ||
| TSBAb(%) | 99 | 97 | |||||||||
| Cohort 3 (75 mg) |
7 | TRAB (IU/L) | 1.2 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 |
| TSAb (%) | 629 | 125 | 132 | 129 | 134 | 124 | 117 | 134 | 124 | ||
| TSBAb (%) | 0 | 100 | 97 | ||||||||
| 8 | TRAB (IU/L) | 8.2 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | |
| TSAb (%) | 791 | 116 | 139 | 140 | 139 | 148 | 141 | 119 | 133 | ||
| TSBAb (%) | 0 | 98 | 96 | ||||||||
| 9 | TRAB (IU/L) | 21.7 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | 39.3 | |
| TSAb (%) | 2,132 | 117 | 129 | 132 | 160 | 140 | 121 | 125 | 167 | ||
| TSBAb (%) | 98 | 97 | |||||||||
| Cohort 4 (150 mg) |
10 | TRAB (IU/L) | 4.6 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 |
| TSAb (%) | 1,781 | 105 | 115 | 125 | 109 | 121 | 126 | 124 | 119 | ||
| TSBAb (%) | 100 | 99 | |||||||||
| 11 | TRAB (IU/L) | 1.2 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | |
| TSAb (%) | 134 | 128 | 136 | 120 | 117 | 115 | 127 | 131 | 143 | ||
| TSBAb (%) | 0 | 98 | 97 | ||||||||
| 12 | TRAB (IU/L) | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | ≥40.1 | |
| TSAb (%) | 6,429 | 130 | 155 | 140 | 140 | 163 | 162 | 164 | 152 | ||
| TSBAb (%) | 96 | 98 |
The median (range) pre-treatment TSAb level was 797% (126%–6,429%). By Day 7 post- K1-70TM administration, the median TSAb level was 125% (105%–146%). Four cases with weakly positive pre-treatment TSAb levels (below 160%) had median TSAb levels of 139% (126%–155%), and they had remained relatively stable at Day 7 when the median level was 126.5% (110%–146%). In the remaining eight cases, the median pre-treatment TSAb level was 1,515.5% (629%–6,429%) and was markedly suppressed to 124% (105%–135%) by Day 7. Exceptionally high pre-treatment TSAb levels (above 2,000%) of 2,132%, 6,006%, and 6,429%, respectively, were recorded in three subjects. They had received K1-70TM doses of 75 mg, 25 mg, and 150 mg, respectively, and their TSAb levels had decreased to 117%, 135%, and 130% on Day 7. Even at the 25 mg dose, the TSAb level decreased from 6,006% to 135%.
The results for the course of changes in TSAb levels showed that in Case 2, they had increased to 418% on Day 70, but on Day 100 had returned to 732%, the pre-K1-70TM administration value (Fig. 3). In Case 4, the TSAb levels were suppressed from a pre-administration level of 6,006% to near the cutoff value until Day 70, but had risen to 285% on Day 100. With the exception of these two cases, the TSAb levels remained suppressed to near the cutoff value until Day 100.
TSBAb was measured on Day 7 and Day 100. On Day 7, the TSBAb level of every subject was elevated. In Cohort 1, the TSBAb levels had become negative by Day 100. In Cohort 2, one subject had a negative TSBAb level on Day 100, but the level in the other two subjects remained strongly positive. In Cohorts 3 and 4, the TSBAb levels were strongly positive on both Day 7 and Day 100.
Changes in ProptosisThe ophthalmopathy in all of the subjects in this trial was in the inactive phase.
At screening, the median degree of proptosis was 17.5 mm in both eyes, and the range was 13–24 mm. On Day 14, Day 42, Day 70, and Day 100 following K1-70TM administration, the median proptosis measurements in the left eye were 17 mm (13–24), 17 mm (12–24), 16.5 mm (11–24), and 16.5 mm (12–23), respectively, and in the right eye they were 16.5 mm (13–23), 16.5 mm (12–22), 16.5 mm (10–22), and 17 mm (11–22), respectively (Table 5). By Day 100, an improvement in proptosis was observed in 12 of the 24 eyes in comparison with when screened, while 10 eyes showed no change, and the proptosis had become worse in the other 2 eyes (sign test, p = 0.0129).
| Cohort | Subject No. | Eye | Screening (mm) | Day 14 (mm) | Day 42 (mm) | Day 70 (mm) | Day 100 (mm) | a Screening - Day 100 (mm) |
|---|---|---|---|---|---|---|---|---|
| Cohort 1 | 1 | Left | 19 | 18 | 18 | 18 | 18 | 1 |
| Right | 19 | 18 | 18 | 18 | 17 | 2 | ||
| 2 | Left | 16 | 14 | 16 | 14 | 14 | 2 | |
| Right | 16 | 15 | 15 | 14 | 14 | 2 | ||
| 3 | Left | 14 | 14 | 14 | 14 | 14 | 0 | |
| Right | 14 | 14 | 14 | 14 | 14 | 0 | ||
| Cohort 2 | 4 | Left | 19 | 20 | 18 | 19 | 19 | 0 |
| Right | 19 | 19 | 18 | 19 | 19 | 0 | ||
| 5 | Left | 14 | 13 | 12 | 14 | 14 | 0 | |
| Right | 15 | 15 | 15 | 15 | 15 | 0 | ||
| 6 | Left | 13 | 13 | 14 | 13 | 15 | –2 | |
| Right | 14 | 14 | 14 | 15 | 17 | –3 | ||
| Cohort 3 | 7 | Left | 16 | 16 | 15 | 15 | 14 | 2 |
| Right | 15 | 15 | 15 | 15 | 15 | 0 | ||
| 8 | Left | 21 | 20 | 20 | 20 | 20 | 1 | |
| Right | 22 | 22 | 21 | 21 | 21 | 1 | ||
| 9 | Left | 24 | 24 | 24 | 24 | 23 | 1 | |
| Right | 24 | 23 | 21 | 21 | 20 | 4 | ||
| Cohort 4 | 10 | Left | 13 | 13 | 12 | 11 | 12 | 1 |
| Right | 13 | 13 | 12 | 10 | 11 | 2 | ||
| 11 | Left | 24 | 23 | 22 | 22 | 22 | 2 | |
| Right | 22 | 22 | 22 | 22 | 22 | 0 | ||
| 12 | Left | 20 | 20 | 20 | 21 | 20 | 0 | |
| Right | 20 | 20 | 20 | 20 | 20 | 0 |
aScreening - Day 100 (mm) was calculated by subtracting the eye protrusion at Day 100 from that at screening.
The Graphical Abstract depicts a Phase 1 dose-escalation trial assessing the safety, tolerability, and efficacy of K1-70TM. Patients received single intravenous doses ranging from 5 to 150 mg, which resulted in dose-dependent serum concentrations and significant reductions in TSAb levels. Mild to moderate adverse events were common, although no severe incidents occurred. Furthermore, improvement in TED-associated proptosis was noted in 50% of treated eyes.
In this phase 1 clinical trial, K1-70TM demonstrated a favorable safety profile, predictable pharmacokinetics, minimal immunogenicity, and positive effects on thyroid function and ophthalmopathy, thereby supporting its potential as a candidate for the treatment of GD.
A total of 12 TEAEs, none of which was serious, were observed in 10 participants (83.3%). The only TEAEs that were observed in more than 10% of the subjects were headache, epistaxis, and fatigue, each occurring in 16.7% (2 of the 12 subjects). Common TEAEs in the Phase 1 clinical trial conducted in the UK [12] consist of fatigue (6 of the 18 subjects), lethargy (3 of the18 subjects), and diarrhea (5 of the 18 subjects). While fatigue was observed in both studies, none of the other adverse effects were the same in both studies. The fatigue, a symptom associated with hypothyroidism, was thought to be unrelated to K1-70TM.
No significant immune response to K1-70TM was observed in any of the study participants. This immune tolerance is thought to be attributable to the fact that K1-70TM is a fully human antibody. The results of the physical examinations of all of the participants during the study period were normal, and no significant injection site reactions were observed.
The TSH receptor has been reported to be expressed in various organs and tissues in addition to the thyroid, including the pituitary, hypothalamus, other central nervous system regions, periorbital tissue, the skin, kidneys, adrenal glands, liver, immune cells, blood cells, vascular tissue, adipose tissue, the heart, skeletal muscle, and bones. Although functionality of the TSH receptors in most of these organs and tissues has been described, any physiological significance in most non-thyroid tissue remains a subject of debate at least [13]. Nevertheless, thus far, and to the best of our knowledge based on our literature search, no other organ impairments have been reported in TSBAb-positive hypothyroid patients whose thyroid function has normalized in response to L-thyroxine treatment.
Even if TSBAb blocking of the TSH receptor were to impair other functions besides thyroid hormone synthesis and action related to Thyroid Eye Disease and Pretibial Myxedema, it would be unlikely to result in significant issues for several months. Nonetheless, careful monitoring is essential.
One patient in Cohort 1 tested ADA-positive prior to dosing (Day 1). The positive reaction was likely due to the presence of a pre-existing antibody in the participant’s blood that cross-reacted with K1-70TM and resulted in ADA positivity in the absence of prior exposure to K1-70TM, as is generally known [14]. Confirmation assays on pre-dosing samples were also positive, suggesting that the result was a non-specific response attributable to cross-reactivity. Moreover, no time-dependent increase in antibody titers were observed after administration of K1-70TM, indicating that it did not induce ADA production (immunogenicity).
In this study we observed a dose-dependent increase in the half-life of K1-70TM, with values approaching the expected half-life of human IgG at higher doses. More specifically, the half-life of K1-70TM increased from 281 hours at the 5 mg dose to 498 hours at the 75 mg dose, suggesting a potential saturation of elimination mechanisms at higher concentrations, leading to prolonged systemic exposure. The increase in Tmax at higher doses further indicates that absorption or distribution kinetics may be influenced by the magnitude of the dose. These findings are consistent with the pharmacokinetic profile reported in the UK Phase I trial [12], in which a half-life of approximately 500 hours was noted following intravenous administration. The prolonged half-life at higher doses may have significant clinical implications, potentially allowing for extended dosing intervals and improved patient compliance.
The effects of K1-70TM on thyroid function were found to be minimal at the 5 mg and 25 mg doses, and noticeable effects were observed only at doses of 75 mg and above. A decrease in FT3 was observed as early as Day 2 in some cases, while the decrease in FT4 tended to lag behind. TSH levels exceeded the upper limit of the reference range starting on Day 7. L-Thyroxine was added to manage the rapid onset of hypothyroidism in two of the three cases in Cohort 3 and all three cases in Cohort 4. TSBAb blocks the actions of both TSH and TSAb, and the early decreases in FT3 and FT4 may have been attributable to TSBAb inhibiting the secretion of thyroid hormones synthesized within follicular cells together with the short half-life of FT3 of approximately one day [15]. Since the TSH response lagged behind the decrease in FT3, using FT3 as an indicator for L-thyroxine administration may be more effective in preventing hypothyroidism. In Case 9, the patient developed hypothyroidism and then rapidly transitioned to thyrotoxicosis starting on Day 56. The patient’s TSAb levels were recorded at 121% on Day 56, 125% on Day 70, and 167% on Day 100, and remained well below the pre-K1-70TM administration level of 2,132%, indicating that thyroid hormone synthesis was suppressed. The FT3/FT4 ratio is generally lower in destructive thyroiditis than in hyperthyroidism associated with GD [16]. In Case 9, the FT3/FT4 ratio dropped from 6.1 on Day 1 to 2.2, 2.8, and 3.2 after Day 56, suggesting destructive thyroiditis. The suspected cause of destructive thyroiditis at the time was administration of Inorg I, which had a high inorganic iodine content of 38 mg per tablet.
Differences of up to 4 mm were observed in the measurements made with the Hertel exophthalmometers produced by different manufacturers, and variations of up to 3 mm were found between measurements made with different instruments from the same manufacturer. Although repeated measurements with the same instrument showed variations within 0.5 mm [17], this falls well within the clinically acceptable threshold, as a variation of less than 1 mm between observers is considered equivalent. The measurements in this study were made on 9 cases at one facility and on the other 3 cases at a different facility, and all of the measurements were performed by skilled assessors, suggesting minimal inter-observer variation. Proptosis was measured at screening and on Day 100, and the results of a sign test showed that the difference was statistically significant. All cases in this study were in the inactive phase of TED, indicating that TSBAb may also be effective in managing inactive phase ophthalmopathy. Although the reduction in proptosis was statistically significant, the clinical relevance of a median reduction of less than 1 mm warrants further investigation. Improvement in proptosis following a single dose of K1-70TM during the inactive phase was also observed in the Phase 1 trial conducted in the UK [12], indicating its potential as a treatment for ophthalmopathy.
TSAb has been reported to be clinically associated with TED [18, 19]. Krieger et al. [20] reported finding that the thyroid stimulating monoclinal antibody M22 promotes hyaluronan (HA) secretion in orbital fibroblasts through crosstalk between TSHR and IGF1R. They suggested that Teprotumumab inhibits HA secretion by blocking TSHR/IGF1R crosstalk through IGF1R. K1-70TM has been shown to suppress HA secretion by inhibiting M22TM binding to TSHR, which also reduces HA production independently of IGF1R. Orbital decompression surgery has been reported to yield an average improvement in exophthalmos of 4.1 ± 1.3 mm. This improvement corresponds to the removal of an average volume of 4.5 ± 1.1 mL of orbital fat [21], based on clinical studies, and an increase in orbital volume by 2.2 ± 0.9 cm3 has been shown to reduce exophthalmos by 2.4 ± 1.9 mm [22]. Removal of approximately 1 mL of fat tissue is generally required to achieve a 1 mm improvement in exophthalmos. The improvement in exophthalmos observed in response to K1-70TM administration is likely to be due, in part, to its inhibitory effect on HA secretion.
Future studies will be needed to validate these preliminary findings, and expanded clinical trials will need to include a larger patient population, with a focus on patients with active TED to assess both patient-reported outcomes, such as in regard to quality of life assessed with a TED-QoL questionnaire [23], and clinician-reported outcomes, including in regard to exophthalmos measurements, eyelid aperture, and extraocular muscle function. Moreover, repeat dosing trials should be conducted to evaluate the efficacy and long-term safety of K1-70TM in comparison with standard therapies for GD and TED.
In conclusion, the consistent pharmacokinetic/pharmacodynamic relationship and the promising safety profile of K1-70TM indicate that it has considerable potential as a safe and effective TSH receptor-targeted therapy for GD patients, especially patients with associated ophthalmopathy.
Nippon Smith Yakuhin Kabushiki Kaisha was the study sponsor and funded the study, and no external funding was received. Nippon Smith Yakuhin Kabushiki Kaisha participated in study design, the collection and analysis of the data, and the production of the Clinical Study Report.
Bernard Rees Smith is a Director of Nippon Smith Yakuhin Kabushiki Kaisha and an employee of RSR Ltd., a manufacturer of diagnostic kits, including those for measuring TSH receptor autoantibodies.
Conceptualization, T.T. and B.R.S.; Data curation, N.W., M.K., Y.I., T.T., U.Y., A.K., T.I. and J.Y.N.; Formal analysis, J.Y.N. and T.T.; Project administration, T.T. and J.Y.N.; Supervision, B.R.S. and K.I.; Writing of the original draft, J.Y.N.
This study was funded and supported by Nippon Smith Yakuhin Kabushiki Kaisha, which participated in the study design, data collection, and analysis. The authors declare no additional conflicts of interest beyond those disclosed.
Co-authors Natsuko Watanabe and Tetsuya Tagami serve as Editors for the Endocrine Journal.
