Protocol for a phase 2 study of bosutinib for amyotrophic lateral sclerosis using real-world data: induced pluripotent stem cell-based drug repurposing for amyotrophic lateral sclerosis medicine (iDReAM) study

Abstract

Introduction

Amyotrophic lateral sclerosis (ALS) is a progressive, severe neurodegenerative disease caused by motor neuron death. Development of a medicine for ALS is urgently needed, and induced pluripotent cell-based drug repurposing identified a Src/c-Abl inhibitor, bosutinib, as a candidate for molecular targeted therapy of ALS. A phase 1 study confirmed the safety and tolerability of bosutinib in a 12-week treatment of ALS patients. The objectives of this study are to evaluate the efficacy and longer-term safety of bosutinib in ALS patients.

Methods and analysis

An open-label, multicentre phase 2 study was designed. The study consisted of a 12-week observation period, a 1-week transitional period, a 24-week study treatment period and a 4-week follow-up period. Following the transitional period, patients whose total Revised ALS Functional Rating Scale (ALSFRS-R) score declined by 1 to 4 points during the 12-week observation period were to receive bosutinib for 24 weeks. In this study, 25 ALS patients will be enrolled; patients will be randomly assigned to the following groups: 12 patients in the 200 mg quaque die (QD) group and 13 patients in the 300 mg QD group of bosutinib. The safety and exploratory efficacy of bosutinib in ALS patients for 24 weeks will be assessed. Efficacy using the ALSFRS-R score will be compared with the external published data from an edaravone study (MCI186-19) and registry data from a multicentre ALS cohort study, the Japanese Consortium for Amyotrophic Lateral Sclerosis Research.

Ethics and dissemination

This study was approved by the ethics committees of Kyoto University, Tokushima University, Kitasato University, Tottori University, Nara Medical University School of Medicine, Toho University and Hiroshima University. The findings will be disseminated in peer-reviewed journals and at scientific conferences.

Trial Registration number

jRCT2051220002; Pre-results, NCT04744532; Pre-results

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• This is a clinical trial for developing molecular-targeted therapies for amyotrophic lateral sclerosis based on the pathophysiology of the disease.

• This clinical trial has a distinctive design that uses two sets of real-world data to assess its efficacy.

• Limitations are that this is an open-label, exploratory study with a small number of patients.

Introduction

Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease caused by the death of motor neurons displaying progressive skeletal muscle weakness. Progression of the disease is rapid, and patients will experience a total loss of spontaneous motor function including respiratory function, with a survival period of 2–5 years after the appearance of initial symptoms without the introduction of a mechanical ventilator. Although the disease mechanism of ALS is still not fully understood, its pathological characteristics consist of motor neuron death and accumulation of misfolded proteins.

By the use of ALS patient induced pluripotent stem cells (iPSCs), we previously reported that a Src/c-Abl inhibitor, bosutinib, decreased the accumulation of misfolded proteins and inhibited the death of motor neurons.¹ Bosutinib improved the impaired autophagy, reduced the accumulation of misfolded proteins and attenuated the energy shortage of ALS patient iPSC-derived motor neurons.¹ Furthermore, treatment with bosutinib reduced the ALS-related phenotypes of ALS model mice.^{1 2} Based on these findings, we hypothesised that the use of bosutinib as a molecular targeted therapy would attenuate the progression of motor symptoms in ALS patients.

Bosutinib is a selective inhibitor of Src/c-Abl tyrosine kinase, and it is used for the treatment of chronic myelogenous leukaemia (CML). It is approved for the treatment of patients with Philadelphia chromosome-positive chronic, accelerated or blast phase CML resistant/intolerant to prior therapy, and patients with newly diagnosed chronic phase CML by the US Food and Drug Administration. Although known frequent adverse effects include diarrhoea, thrombocytopaenia and liver transaminase elevations, from the results of past clinical trials with CML patients,³ it became apparent that the safety of bosutinib is feasible.³ However, because the disease-related physical conditions of ALS patients differ from those of CML patients, evaluation of the safety and tolerability of bosutinib in ALS patients was conducted as a phase 1 clinical trial.^{4 5} The results of that phase 1 study showed that bosutinib treatment with up to 300 mg was generally safe and well tolerated in patients with ALS, and a potential signal of efficacy was observed (submitted). A phase 2 clinical trial is now planned to evaluate the efficacy and long-term (24 weeks) safety of bosutinib in a larger number of ALS patients.

Clinical trials are usually conducted as randomised controlled trials (RCTs) against placebo or a relevant drug. Although RCTs with placebo control represent a standard approach in common disorders, the contemporary use of real-world data and real-world evidence is attracting a great deal of attention,6,10 and especially in clinical trials of rare diseases.¹¹ This approach has advantages in such areas as the solution of ethical issues involved in administering placebos in fatal diseases and ensuring statistical power in rare diseases with small numbers of patients. While real-world data has previously been used in clinical oncology trials, it has recently begun to be applied in clinical studies of neurodegenerative diseases.^{12 13} In the present study, efficacy using the motor function score, Revised ALS Functional Rating Scale (ALSFRS-R), will be compared with two types of real-world data—the external published data from an edaravone study (MCI186-19),¹⁴ when edaravone was approved for ALS, and the registry data from a multicentre ALS cohort study, the Japanese Consortium for Amyotrophic Lateral Sclerosis Research (JaCALS).^{15 16}

Methods and analysis

Study design

This is an open label, multicentre, phase 2 study. The efficacy and long-term (24 weeks) safety of bosutinib for the treatment of ALS patients will be evaluated exploratorily.

The following patients including both sporadic ALS and familial ALS will be enrolled in this study.

• ALS patients categorised as either ‘Definite ALS’ or ‘Probable ALS’ in the revised El Escorial (Airlie House) criteria for the diagnosis of ALS.

• Patients at grades 1 or 2 in the Japan ALS Severity Scale of the grant-in-aid programme for chronic diseases from the Japanese Ministry of Health, Labour and Welfare.

• Patients with ALS within 2 years of symptom onset at the time of first registration.

• Patients with a change in total ALSFRS-R score during the observation period of −1 to −4 points.

Detailed eligibility criteria are presented in box 1. To compare the efficacy of the study drug, eligibility criteria related to the ALS background that might affect the efficacy assessment were matched with those of the edaravone study (MCI186-19).

Box 1. Eligibility criteria.

Inclusion criteria:

1. Evidence of a personally signed and dated informed consent document indicating that the patient has been informed of all pertinent aspects of the study, and to be additionally signed by a delegated signer if the patient is unable to handwrite;

2. Patients aged ≥20 years and ≤75 years at the time of procuring informed consent;

3. ALS patients who are categorised as either ‘Definite ALS’ or ‘Probable ALS’ in the El Escorial and revised Airlie House criteria for the diagnosis of ALS;

4. Patients at grades 1 or 2 in the Japan ALS Severity Scale of the grant-in-aid program for chronic diseases from the Japanese Ministry of Health, Labour and Welfare;

5. Patients with ALS within 2 years of symptom onset at the time of first registration;

6. Patients with change in total ALSFRS-R score from −1 to −4 points during the observation period;

7. Patients with score of at least 2 on all items of ALSFRS-R; 4. Writing, 5. Feeding behaviour (1) must have at least 2 points on each side;

8. Negative urine pregnancy test (for females with childbearing potential) at screening;

 Female patients with non-childbearing potential must meet at least 1 of the following criteria:

1. Achieved postmenopausal status defined as follows: cessation of regular menses for at least 12 consecutive months with no other pathological or physiological cause; status may be confirmed with a serum follicle stimulating hormone (FSH) level confirming the postmenopausal state;

2. Have undergone a documented hysterectomy and/or bilateral oophorectomy;

3. Have medically confirmed ovarian failure;

All other female patients (including female patients with tubal ligations) are considered to be with childbearing potential;

• 9 1Patients with appropriate renal function defined as follows at the time of first and second registrations;

  1. Estimated creatinine clearance or eGFR ≥60 mL/min (mild renal impairment) as calculated using the standard method of the institution (the CKD-EPI equation is recommended, but other methods such as Cockcroft-Gault or MDRD may be used. The same method should be applied throughout the study period.);

• 9 2Patients with appropriate hepatic function as defined as follows at the time of the first and second registrations, as follows:

  1. Total serum bilirubin ≤1.5 × ULN unless the patient has documented Gilbert syndrome;

  2. AST and ALT ≤2.5 × ULN;

• 9 3Patients who can consistently take the investigational drug and other oral tablets with water throughout the study period;
• 9 4Patients whose adverse event during previous treatment has recovered to baseline (Visit 5: before the start of study drug administration) or CTCAE v.4.03 ≤ grade 1 at the time of the first and second registrations, excluding the case where the investigator (or sub-investigator) judges that the event is not a safety risk;
• 9 5Willing and able to comply with scheduled visits, treatment plan, laboratory tests and other study procedures.

Exclusion criteria:

1. Patients with tracheostomy;

2. Patients with decreased respiratory function and complaining of dyspnoea at the time of enrollment (one of the three items on the ALSFRS-R related to respiratory (10) dyspnoea, (11) orthopnoea or (12) respiratory failure is less than 3 points);

3. Patients whose %FVCs are at least 80% at the time of first and second registrations;

4. Patients who have nerve conduction study findings of demyelination, such as conduction block;

5. Patients using edaravone within 4 weeks prior to enrollment in the observation period; Patients using edaravone at the time of enrollment in the observation period; Patients who started edaravone after beginning of the observation period;

6. Patients who started riluzole after start of the observation period; Patients who changed the dosage of riluzole after start of the observation period;

7. Patients with bulbar-onset type ALS with dysphagia and/or dysarthria;

8. Patients with Parkinson’s disease and syndromes, schizophrenia, cognitive impairment and other comorbidities that may have a significant impact on the evaluation of drug efficacy;

9. Patients with a history of spinal surgery such as cervical spondylosis or disc herniation after ALS onset, or patients scheduled to undergo surgery during the study period;

10. Patients whose symptoms could not be ruled out as symptoms of a disease requiring a differential diagnosis, such as cervical spondylosis or multifocal motor neuropathy;

11. Pregnant female patients; breastfeeding female patients;

12. History of clinically significant or uncontrolled cardiac disease including:

    • History of, or active, congestive heart failure;

    • Uncontrolled angina or hypertension within 3 months prior to registration;

    • Myocardial infarction within 12 months prior to registration;

    • Clinically significant ventricular arrhythmia (such as ventricular tachycardia, ventricular fibrillation or Torsades de pointes);

    • Diagnosed or suspected congenital or acquired prolonged QT interval history or prolonged QTc (QTcF should not exceed 500 msec);

    • Unexplained syncope;

13. Uncontrolled hypomagnesaemia or uncorrected hypokalaemia due to potential effects on the QT interval;

14. Patient taking the following medicines during study drug administration:

    1. Combination with warfarin or other anticoagulant. Combination with low molecular weight heparin is acceptable;

    2. Src or c-Abl inhibitors;

    3. Drugs known to prolong the QT interval or predispose to Torsades de pointes;

    4. Current or anticipated use of a strong or moderate CYP3A inhibitor or inducer;

    5. Drugs affecting gastric pH such as proton pump inhibitors (eg, lansoprazole);

15. History of malignancy within 5 years prior to the first registration with the exception of basal cell carcinoma or cervical carcinoma in situ, or stages 1 or 2 cancer that is considered adequately treated and currently in complete remission for at least 12 months;

16. Patients enrolled in other clinical studies within 12 weeks before the first registration or are expected to be enrolled in other clinical studies using a study drug during this study;

17. Known prior or suspected severe hypersensitivity to the study drug or any component in its formulations;

18. Patients with active, uncontrolled bacterial, fungal or viral infection, including hepatitis B virus (HBV), hepatitis C virus (HCV), known human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS)-related illness;

19. Recent or ongoing clinically significant GI disorder (eg, Crohn’s disease, ulcerative colitis, or prior total or partial gastrectomy);

20. Patients with chronic obstructive pulmonary disease;

21. Major surgery within 14 days prior to the first registration;

22. Patients who fulfill these conditions:

    1. Neutrophil count (ANC) <1500/mm³ or white blood cell <3000/mm³ at the time of the first and second registrations;

    2. Haemoglobin <9.0 g/dL at the time of the first and second registrations;

    3. Platelet count <100 000/μL at the time of the first and second registrations;

23. Other acute or chronic medical or psychiatric conditions including recent (within the past year) or active suicidal ideation or behaviour or laboratory abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with interpretation of the study results and, in the judgment of the investigator, would make the participant inappropriate for entry into this study;

24. Investigator site staff members directly involved in the conduct of the study and their family members, site staff members otherwise supervised by the investigator, or Pfizer employees, including their family members, directly involved in the conduct of the study.

The study is designed to explore the efficacy and safety of 2 dose levels (200 mg QD and 300 mg QD) of bosutinib for ALS patients during 24 weeks of treatment. The study consists of 4 periods: a 12-week observation period, a 1 week transitional period (±2 days, total 5 to 9 days), a 24-week study treatment period and a 4-week safety follow-up period. After completion of the transitional period, patients whose total ALSFRS-R score decreased by 1 to 4 points during the 12-week observation period will be enrolled in the study treatment period. In this study, 25 ALS patients will be enrolled; patients will randomly be assigned to the following groups: 12 patients to the 200 mg group and 13 patients to the 300 mg group. The target sample size was determined based on the study feasibility perspective. Referring to the mean and the SD values of change from baseline in total ALSFRS-R score observed in an edaravone group in MCI186-19, which were −4.4 and 4.0 respectively, the probabilities that the means of change from baseline in total ALSFRS-R score of 300 mg and 200 mg groups exceed that of external placebo data of −6.8 are computed to be 97.4% and 96.9%, respectively. The efficacy and safety of bosutinib in ALS patients during their 24 weeks of treatment will be assessed. Efficacy using the ALSFRS-R score will also be compared with the published data of a placebo group and an edaravone group in MCI186-19. Because edaravone is an intravenous formulation while bosutinib is administered orally, and it is also necessary to avoid aspiration pneumonia in patients with advanced dysphagia, bulbar-onset type ALS was excluded from the eligibility criteria of this study. Furthermore, bulbar-onset type ALS from the MCI186-19 data will also be excluded for our analysis. In addition, to match the patient background of this study with the patient background of MCI186-19, the patients will be assigned to the 200 mg group or the 300 mg group according to the amount of change in ALSFRS-R during the observation period, the factor with the greatest influence on the efficacy of the investigational drug. By static allocation, approximately 85% of patients in each of the 200 mg and 300 mg groups will have a decrease of 1–2 points in ALSFRS-R and about 15% will have a decrease of 3–4 points in ALSFRS-R, in accordance with the result of MCI186-19. Efficacy using the ALSFRS-R score will also be compared with the matched control of JaCALS, an ALS registry, in an exploratory manner. The matched controls will be selected from JaCALS registry data for cases meeting the inclusion and exclusion criteria of this study and will have a similar patient background. To select matched controls, propensity score matching will be conducted with the following parameters: nearest-neighbour matching (1:2) with covariates of age, disease duration, baseline ALSFRS-R score and ALS severity score. A calliper of 0.2 times the SD of logit of the propensity score.

For patients receiving riluzole prior to entering this study, its continued administration is allowed throughout the study period, although without dosage change. The concomitant use of edaravone is not allowed during the 4 weeks prior to enrollment and throughout the entire study period.

The outline of study design and clinical trial schedule were presented in figure 1 and online supplemental file 1. The informed consent document was shown in online supplemental file 2.

Figure 1. Schema of study design.

Outcomes

Primary endpoints

The primary endpoints are the change from baseline (before start of study drug administration) in ALSFRS-R at week 24 in each of the 200 mg and 300 mg groups, which is compared with the external published data of the placebo group excluding bulbar-onset type in the edaravone study (MCI186-19), and the safety in each dose group and pooled dose group (200 mg and 300 mg groups) during 24 weeks of treatment. Adverse events classified according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE v.4.03), laboratory test abnormal, vital signs, ECG and chest X-ray findings will be evaluated.

Secondary endpoints

The secondary endpoints are the change from baseline in ALSFRS-R at week 24 in the combined 200 mg and 300 mg group compared with the external published data of the placebo group (excluding bulbar-onset type in the edaravone study, MCI186-19), and the change from baseline in ALSFRS-R at week 24 in the combined 200 mg and 300 mg group compared with the external published data of the edaravone group (excluding bulbar-onset type in the edaravone study, MCI186-19).

Exploratory endpoints

In the exploratory endpoints, change from baseline in ALSFRS-R at week 24 is compared with external controls matched for clinical background in the JaCALS registry. Changes from baseline in the modified Norris Score, ALSAQ-40, %FVC and grip power are compared with those of the placebo group in the edaravone study (MCI186-19). Biomarkers such as blood neurofilament L (NFL), blood albumin and blood creatinine/cystatin C during the observation period and the study treatment period are evaluated. Evaluation of the correlation between plasma NFL levels and changes in ALSFRS-R and comparison of the changes in ALSFRS-R score between the high and low plasma NFL groups divided by the plasma NFL level at baseline will also be conducted.

Data analysis and statistical method

As for the efficacy of primary and secondary endpoints, in ALS patients enrolled and receiving at least 1 dose of bosutinib, the mean change from baseline in ALSFRS-R at week 24 of the 200 mg group, the 300 mg group and the dose-combined group of bosutinib will be compared with the mean change from baseline of the placebo group or edaravone group (except for the bulbar-onset type in the edaravone study, MCI186-19), respectively. The mean change from baseline in ALSFRS-R at week 24 of the 200 mg and 300 mg groups of bosutinib will be compared with that of the placebo group in edaravone study, MCI186-19 (excluding participants with bulbar-onset ALS in study MCI186-19). The average value of the placebo group in the assessment results will be used for the comparison. Missing data on change from baseline in ALSFRS-R at week 24 will be imputed by last observation carried forward (LOCF) only if the patient drops out of the study after week 12. Mixed-effects model repeated measures (MMRM) analysis, in which the response variable is the change from baseline in ALSFRS-R, will be conducted for each dose group. No imputation of missing data will be performed in the MMRM analysis. For safety analysis, in ALS patients enrolled and receiving at least 1 dose of bosutinib, the frequencies of adverse events, abnormal laboratory tests, abnormal vital signs, ECG and chest X-ray findings during the study treatment period will be analysed for each dose group and the pooled dose group. The timing of onset, details, severity and relationship to the study drug will be summarised.

Patient and public involvement

The patients and/or the public were not involved in the design of this study.

Registration

The planning of this study extended from April 2022 to May 2023, with seven participating sites in Japan.

Ethics and dissemination

This study was approved by the Institutional Review Boards of Kyoto University, Tokushima University, Kitasato University, Tottori University, Nara Medical University, Toho University and Hiroshima University. This study was registered with jRCT (jRCT2051220002) and ClinicalTrial.gov (NCT04744532). The findings from this study will be disseminated through presentations at conferences and publications in peer-reviewed journals.

Data availability statement

No data are available.