Minocycline for sporadic and hereditary cerebral amyloid angiopathy (BATMAN): study protocol for a placebo-controlled randomized double-blind trial

This is an exploratory study. Our study design is a randomized double-blind placebo-controlled trial with minocycline treatment versus placebo for 3 months in 60 participants (30 with D-CAA and 30 with sporadic CAA). At baseline (t = 0), a standardized neuropsychological assessment will be performed (Fig. 1). At t = 1 and t = 3 months, we will perform the following study procedures: CSF sample collection, collection of demographics, neurological examination, blood sample collection, and 7-T MRI (Fig. 1). In-between study visits, a short questionnaire on side effects and compliance will be sent to enhance participant retention.

The inclusion criteria for the participants with D-CAA are the age of 18 years and older and genetically proven D-CAA. For participants with sporadic CAA, we used the modified Boston criteria [17]. Furthermore, all participants should have no more than two ICHs (with the occurrence of the last ICH at least 1 year ago, to ensure that inflammation in the acute stage of ICH is stabilized). Also, all participants should have at least two lobar microbleeds or cortical superficial siderosis on MRI. With these criteria, we hope to include participants with moderate CAA pathology but not yet severe.

The exclusion criteria are a previous allergic reaction to minocycline, a modified Rankin Scale score of at least 3, contraindications for 7-T MRI (e.g., claustrophobia, pacemakers, and ferromagnetic implants), contraindications for lumbar puncture (e.g., compression of the spinal cord, a coagulopathy or thrombocytopenia < 100), pregnancy or breastfeeding, liver or renal failure, use of antibiotics 1 month prior of participation, systemic lupus erythematosus or other diseases known to generate inflammatory responses, and use of drugs that are contraindicated in combination with minocycline (e.g., carbamazepine).

There will be a block randomization by computer for both forms of CAA to ensure 15 participants in each group (D-CAA 15 minocycline and 15 placebo, sporadic CAA 15 minocycline and 15 placebo). Minocycline will be administered orally twice a day 100 mg (total daily dose = 200mg) for 3 months.

The pharmacy of the LUMC will perform block randomization by computer, generate the allocation sequence, and blindly repackage the products. Everyone except the pharmacy will be blinded (trial participants, care providers, outcome assessors, and data analysts). After the termination of the study and analysis of the data, data analysts and trial participants will be unblinded.

Our primary outcome measures are CSF biomarkers of inflammation, vessel integrity, and the gelatinase pathway with emphasis on IL-6, MCP-1, IBA-1, MMP2/9, and VEGF. CSF is collected at t = 0 and t = 3 months.

The secondary endpoints include the safety and tolerability of minocycline and hemorrhagic markers on 7-T MRI and serum biomarkers. These data are collected at t = 0 and t = 3 months. Furthermore, we will use the collected data to obtain information on the stability and natural variation of different CSF biomarkers and blood biomarkers in patients with CAA over time.

This is an exploratory study, and a formal power calculation is difficult as the levels of inflammatory CSF biomarkers in D-CAA or sporadic CAA are not well known. In our D-CAA-cohorts, previous CSF analyses of amyloid-beta 40 and 42 and a biomarker panel including, e.g., VEGF, showed that patients could be distinguished from controls with group sizes as small as 15 [18]. In stroke patients, there was a high correlation between serum levels of IL-6 and MMP-9 and the occurrence of microbleeds [19, 20]. Previous animal studies using minocycline showed a 30–70% reduction in relevant biomarkers such as MMP-9 and gliosis on a tissue level [13, 15]. In our data, VEGF levels in CSF showed a twofold increase in patients compared with controls (6.5 ± 2.8 vs 3.2 ± 2.2 pg/ml). Assuming a similar effect size of 50% change after treatment (power of 0.8, alpha = 0.05), the calculated group size would be 14. As the effect may be less robust compared to the animal model, we chose a group size of 30 participants, which would yield sufficient power to detect a 30% change, based on the preliminary data. Individual subjects will be replaced after withdrawal. Outcome data for all included participants will be collected.

We will perform descriptive statistics for the prevalence of different biomarkers in CSF (and MR imaging) and their evolution over time with disease progression.

Because minocycline targets multiple pathways (including inflammatory, vessel integrity, and gelatinase pathways) that play a role in CAA, we chose multiple CSF biomarkers to cover all three pathways. We will compare the level of inflammatory biomarkers between the treated and not treated groups with regression analyses, adjusted for age and sex. In the exploratory subgroup analyses, we will stratify for D-CAA and sporadic CAA and will use repeated measurements analyses, as well as use a single primary composite measure [21, 22]. Since this is an exploratory study, we will not correct for multiple testing for the 5 (IL-6, MCP-1, IBA-1, MMP2/9, and VEGF) co-primary endpoints.

There is no anticipated harm and compensation for trial participation.