Long-term follow-up of patients treated with caplacizumab and safety and efficacy of repeat caplacizumab use: Post-HERCULES study

Preventative and therapeutic effects of a novel humanized anti-glycoprotein Ibα fragment of antigen-binding region in a murine model of thrombotic thrombocytopenic purpura

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a potentially fatal blood disorder resulting from severe deficiency of plasma ADAMTS-13 activity. Current treatment for immune-mediated TTP includes daily therapeutic plasma exchange plus caplacizumab and immunosuppressives. For hereditary TTP resulting from mutations of ADAMTS-13, plasma infusion or recombinant ADAMTS-13 is the treatment of choice. However, there are still unmet needs for an effective alternative therapy for TTP.

OBJECTIVES

The present study aimed to evaluate the therapeutic efficacy of a novel humanized antibody fragment of antigen binding against platelet glycoprotein Ibα (CA1001) in a murine model of TTP.

METHODS

Platelet agglutination profiles, microfluidic shear-based assay, intravital microscopy thrombosis model, and lysine histone-induced murine "TTP-like" model were employed.

RESULTS

CA1001 exhibited potent inhibition of botrocetin-induced murine platelet agglutination in a dose- and time-dependent manner. CA1001 also significantly inhibited shear-dependent adhesion and aggregation of murine platelets to endothelial von Willebrand factor (VWF) released from calcium ionophore-activated cremaster venules in Adamts-13 null mice and blocked the formation of platelet-VWF rich thrombosis. More importantly, CA1001 appeared to be efficacious in preventing and treating a histone-induced "TTP-like" syndrome in Adamts-13 null mice, demonstrated by the alleviation of thrombocytopenia, prerenal injury, and formation of microvascular thrombosis in major organ tissues.

CONCLUSION

CA1001 can effectively inhibit VWF-platelet interaction and thrombus formation under various (patho)physiological conditions. Thus, CA1001 may be a potential candidate for further development as a novel therapeutic for immune-mediated and hereditary TTP and perhaps for other inflammatory thrombotic disorders such as ischemic stroke.

Caplacizumab treatment in elderly patients with iTTP: Experience from the Spanish TTP Registry

Immune thrombotic thrombocytopenic purpura (iTTP) typically affects middle-aged individuals, although it sometimes appears in older patients. Caplacizumab is approved for the treatment of iTTP, but information on the safety and efficacy of this drug in elderly patients is not available. We aimed to analyze the management and outcomes of iTTP patients registered in the Spanish TTP Registry and receiving caplacizumab at any time during the acute episode, focusing on patients ≥60 years (n = 29) and comparing them with patients <60 years (n = 70). Severe bleeding motivated caplacizumab's initiation delay in one patient ≥60 years. Patients receiving anticoagulation or antiplatelet therapy at diagnosis were more common in older patients (10% vs. 1%; p = 0.074), as well as the occurrence of bleeding motivating caplacizumab discontinuation (17% vs. 1%, respectively; p = 0.008). Caplacizumab seemed to be efficient in the treatment of iTTP in older patients, reducing refractoriness and death to 3% and exacerbation to 10%, similar to younger patients. The higher risk of bleeding in this older population warrants the need for close monitoring during treatment and to further explore the best management of thrombotic and bleeding risk.

Multicenter Prospective Pilot Study Identifying Thrombomodulin as a Potential Biomarker for Neurocognitive Outcomes in Immune Thrombotic Thrombocytopenic Purpura

Background/Objectives: Immune thrombotic thrombocytopenic purpura (iTTP) is a rare, chronically relapsing disorder that causes life-threatening thrombotic microangiopathy. Many survivors in clinical remission show evidence of ongoing silent cerebral infarction and neurocognitive deficits. Prospective longitudinal studies of this population are needed to acquire a complete understanding of the mechanism behind this ongoing neurologic injury. We aimed to assess the feasibility of a multicenter prospective study of neuropsychological and cognitive function in iTTP survivors in remission and examine novel biomarkers. Methods: We aimed to enroll 50 iTTP patients across three USTMA consortium sites between 2019 and 2022 in a 24-month longitudinal study. Clinical, cognitive, and biomarker assessments, including ADAMTS13 activity, were performed. Results: Despite the COVID-19 pandemic, we enrolled 38 subjects, and 31 (81.6%) completed closeout evaluations at 24 months. Upon the participants' enrollment in the study, we confirmed previous findings, including high rates of moderate to severe neurocognitive and psychiatric sequelae (anxiety, 47%; depression, 45%; and headaches, 55%). Changes in cognitive function were measurable and included decreased immediate memory and visuospatial abilities. Over this two-year study, we did not see a significant change in neurocognitive findings. There was no association between cognitive function and ADAMTS13 activity; however, we found that the level of soluble thrombomodulin (CD141) was significantly correlated with cognitive impairment. Conclusions: We conclude that a more extensive study is feasible, and at least 5-10 years may be required to detect trends in neurocognitive function. Soluble thrombomodulin is a promising biomarker for cognitive impairment in survivors of iTTP, and it is worthy of additional study.

Complex immunogenicity assessment in caplacizumab-treated patients with immune-mediated thrombotic thrombocytopenic purpura who have received plasma exchange

Background

International Society on Thrombosis and Haemostasis guidelines for immune-mediated thrombotic thrombocytopenic purpura (iTTP) treatment recommend concurrent therapeutic plasma exchange (TPE), immunosuppressive therapy (IST), and caplacizumab. TPE can complicate antidrug antibody (ADA) measurements by transferring pre-existing antibodies (pre-Abs) into patients via donor plasma and/or diluting treatment-emergent (TE) ADAs.

Objectives

To assess the presence of ADAs in patients with iTTP who received caplacizumab.

Methods

Immunogenicity data from patients with iTTP receiving caplacizumab once daily plus TPE/immunosuppressive therapy in 4 clinical trials (TITAN, HERCULES, Post-HERCULES, and a trial conducted in Japanese patients) in the clinical development program were analyzed. ADA and modified ADA assays differentiated pre-Abs from TE ADAs. A functional neutralizing antibody (NAb) assay and a neutralizing epitope characterization assay (NECA) assessed the presence of ADAs with neutralizing potential. The impact of ADAs on efficacy, pharmacokinetics/pharmacodynamics, and safety was evaluated.

Results

Among 228 patients in 4 studies, prevalence of pre-Abs ranged from 17.1% (TITAN) to 56.7% (HERCULES), while TE ADA prevalence ranged from 3.1% (HERCULES) to 14.3% (Japanese study). The TE NAb-positive rate ranged from 0% (Japanese study) to 12% (Post-HERCULES) using the functional NAb assay and from 2.7% (Post- HERCULES) to 14.3% (Japanese study) using the NECA. The presence of these antibodies did not impact treatment efficacy or safety.

Conclusion

A complex immunogenicity assay strategy was required to define the pre-Ab/TE ADA status of patients with iTTP treated with caplacizumab in a clinical trial setting. In addition to the wide range of pre-Abs observed, few patients had detectable TE ADAs or NAbs, neither of which affected efficacy/safety.

Discovery of nanobodies: a comprehensive review of their applications and potential over the past five years

Nanobodies (Nbs) are antibody fragments derived from heavy-chain-only IgG antibodies found in the Camelidae family as well as cartilaginous fish. Their unique structural and functional properties, such as their small size, the ability to be engineered for high antigen-binding affinity, stability under extreme conditions, and ease of production, have made them promising tools for diagnostics and therapeutics. This potential was realized in 2018 with the approval of caplacizumab, the world's first Nb-based drug. Currently, Nbs are being investigated in clinical trials for a broad range of treatments, including targeted therapies against PDL1 and Epidermal Growth Factor Receptor (EGFR), cardiovascular diseases, inflammatory conditions, and neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. They are also being studied for their potential for detecting and imaging autoimmune conditions and infectious diseases such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A variety of methods are now available to generate target-specific Nbs quickly and efficiently at low costs, increasing their accessibility. This article examines these diverse applications of Nbs and their promising roles. Only the most recent articles published in the last five years have been used to summarize the most advanced developments in the field.

A Simple Analysis of the Second (Extra) Disulfide Bridge of VHHs

Camelids produce a special type of antibody, known as VHHs, that has lost the VL domain, providing a more optimised VH domain. This particular highly stable antibody domain has interesting properties for biotechnological development. Ordinarily, those molecules possess only one disulphide bridge, but surprisingly, at least a quarter of these VHHs have a second one. Curiously, this does not seem to be essential for the stability and the function of this domain. In an attempt to characterise precisely the role and impact of this disulphide bridge at the molecular level, several in silico mutants of a VHH were created to disrupt this second disulphide bridge and those systems were submitted to molecular dynamics simulation. The loss of the second disulphide bridge leads to an increase in the flexibility of CDR1 and CDR3 and an unexpected rigidification of CDR2. Local conformational analysis shows local differences in the observed protein conformations. However, in fact, there is no exploration of new conformations but a change in the equilibrium between the different observed conformations. This explains why the interaction of VHHs is not really affected by the presence or absence of this second bridge, but their rigidity is slightly reduced. Therefore, the additional disulphide bridge does not seem to be an essential part of VHHs function.

Long-term health-related quality of life and mental health in patients with immune thrombotic thrombocytopenic purpura

Immune thrombotic thrombocytopenic purpura (iTTP) is a rare and potentially life-threatening disorder. Treatment advances have lowered morbidity rates, but past acute events can still cause long-term consequences, reducing health-related quality of life (HRQoL) and determining cognitive impairment, anxiety, and depression. We aimed to investigate these aspects and the role of caplacizumab and rituximab: 39 patients were evaluated using the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36), the FACIT-Fatigue, the Hospital Anxiety and Depression Scale, and the Functional Assessment in Cancer Therapy-Cognitive Function questionnaires. The median age at study inclusion was 50 years (IQR 38-60), and the median follow-up from diagnosis was 97 months (IQR 14-182); 82% of patients were female, and 36% had one or more recurrences. Caplacizumab was administered in 16 patients (41%), as well as rituximab. ITTP patients reported lower physical and mental HRQoL scores than the general population. No differences in physical or mental domains were observed between patients treated or not with caplacizumab, while those who received rituximab reported lower scores in mental health. Neurological impairment at diagnosis correlated with worse fatigue. The majority of patients (72%) reported anxiety or depression (82%). ITTP had a significant impact on the long-term cognitive function, fatigue, depression, and anxiety levels of patients, with a negative effect on their HRQoL. Our findings underscore the need to pay special attention to patients' long-term physical and mental health, regardless of the medical treatments received.

Efficacy and relative safety of caplacizumab in immune-mediated thrombotic thrombocytopenic purpura: a systematic review and meta-analysis

Immune-mediated thrombotic thrombocytopenia purpura (iTTP) is a rare microvascular disease characterized by severe disseminated microvascular thrombose-bleeding syndrome. Caplacizumab has been approved for the treatment of iTTP in combination with Plasma Exchange (PE) and immunosuppressive therapy, but its role in iTTP therapy remains uncertain. Therefore, we conducted a meta-analysis to investigate the safety and efficacy of caplacizumab for the treatment of patients with iTTP. We searched electronic databases (PubMed, Embase, Cochrane Library, and Scopus) and reference lists of relevant articles to find articles published from 2015 to 2022. The time to normalization of the platelet count of the group caplacizumab is shorter than the group placebo (SMD = -0.72; 95% CI -0.88 to -0.56; P  < 0.05). Caplacizumab reduced the incidence of mortality (OR = 0.41; 95% CI 0.18-0.92; P  < 0.05), exacerbations (OR = 0.10; 95% CI 0.05-0.18; P  < 0.05), and recurrence (OR = 0.17; 95% CI 0.06-0.50; P  < 0.05). However, the bleeding events in the caplacizumab group were higher than those in the placebo group, especially severe bleeding events. There was no difference in ADAMTS13 activity and thromboembolic events between the two groups. Our analysis indicated that caplacizumab is effective and well tolerated for the treatment of iTTP.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022362370.

ADAMTS13 recovery in acute thrombotic thrombocytopenic purpura after caplacizumab therapy

ABSTRACT

Caplacizumab prevents the interaction between von Willebrand factor and platelets and is used to treat immune thrombotic thrombocytopenic purpura (iTTP). Its administration has been associated with a delay in ADAMTS13 activity restoration after plasma exchange (PEX) suspension. We analyzed the outcomes of 113 iTTP episodes, 75 of which were treated with caplacizumab, in 108 patients from the Spanish Registry of Thrombotic Thrombocytopenic Purpura. Caplacizumab shortened the time to platelet count normalization and reduced PEX requirement, exacerbations, and relapses. There was no difference in the time to achieve ADAMTS13 activity ≥20% after PEX end between caplacizumab-treated and nontreated episodes (median [interquartile range], 14.5 [7.7-27.2] vs 13.0 [8.0-29.0] days, P = .653). However, considering the 36 episodes in which caplacizumab was started ≤3 days after iTTP diagnosis, the time for ADAMTS13 restoration from PEX end was higher than in those episodes in which caplacizumab was started >3 days after iTTP diagnosis (20.0 [12.0-43.0] vs 11.0 [3.5-20.0] days, P = .003) or than in non-caplacizumab-treated episodes (P = .033). This finding could be related to a significantly shorter duration of PEX in early caplacizumab-treated episodes than in late caplacizumab-treated episodes (5.5 [4.0-9.0] vs 15.0 [11.0-21.5] days, P < .001) or non-caplacizumab-treated episodes (11.0 [6.0-26.0] days, P < .001). There were no differences in time to ADAMTS-13 restoration from PEX start (28.0 [17.2-47.5], 27.0 [19.0-37.5] and 29.5 [15.2-45.0] days in early caplacizumab-treated, late caplacizumab-treated and non-caplacizumab-treated episodes). Early administered caplacizumab does not prevent the requirement for immunosuppression but has beneficial effects by shortening PEX requirement without major safety concerns.

Should we consider caplacizumab as routine treatment for acute thrombotic thrombocytopenic purpura? An expert perspective on the pros and cons

INTRODUCTION

Immune thrombotic thrombocytopenic purpura (iTTP) is a rare and life-threatening disorder. Caplacizumab has been the latest drug incorporated into the initial treatment of acute episodes, allowing for faster platelet recovery and a decrease in refractoriness, exacerbation, thromboembolic events, and mortality. However, caplacizumab is also associated with a bleeding risk and higher treatment costs, which prevent many centers from using it universally.

AREAS COVERED

Studies that included iTTP and/or caplacizumab to date were selected for this review using PubMed and MEDLINE platforms. We describe outcomes in the pre-caplacizumab era and after it, highlighting the benefits and risks of its use early in frontline, and also pointing out special situations that require careful management.

EXPERT OPINION

It is clear that the availability of caplacizumab has significantly and favorably impacted the management of iTTP patients. Whether this improvement is cost-effective still remains uncertain, and data on long-term sequelae and different healthcare systems will help to clarify this point. In addition, evidence of the bleeding/thrombotic risk of iTTP patients under this drug needs to be better addressed in future studies.

Caplacizumab for immune thrombotic thrombocytopenic purpura: real-world multicenter data

Given the limited real-world data of caplacizumab, our multicenter real-world study was designed to assess the safety and efficacy of caplacizumab in immune thrombotic thrombocytopenic pupura (iTTP), compared to historic controls. We have studied 70 patients: 23 in the caplacizumab and 47 in the historic control group. Plasma exchange was applied in all episodes except for two patients that denied plasma exchange. Rituximab as first-line treatment was more common in the caplacizumab group compared to historic control. Caplacizumab (10 mg daily) was given at a median on day 7 (1-43) from initial diagnosis for 32 (6-47) dosages. In the caplacizumab group, a median of 12 (8-23) patients required plasma exchange sessions versus 14 (6-32) in the control group. Caplacizumab administration did not produce any grade 3 complications or major hemorrhagic events. After a median of 19.0 (2.6-320) months since the iTTP diagnosis, 5 deaths occurred (4 in the control group and 1 in the caplacizumab group, p = 0.310). Caplacizumab patients achieved early platelet normalization and ADAMTS13 activity normalization at the end of treatment. Relapse was observed only in 2/23 (9%) caplacizumab patients, compared to 29/47 (62%) historic controls (p < 0.001). Overall, caplacizumab is safe and effective in treating iTTP, including cases refractory to plasma exchange, re-administration, and cases without previous plasma exchange treatment. No major hemorrhagic events were observed. Cessation of dosing guided by ADAMTS13 has ensured a low relapse rate.

A novel von Willebrand factor multimer ratio as marker of disease activity in thrombotic thrombocytopenic purpura

Immune-mediated thrombotic thrombocytopenic purpura (iTTP), an autoantibody-mediated severe ADAMTS13 deficiency, is caused by insufficient proteolytic processing of von Willebrand factor (VWF) multimers (MMs) and microvascular thrombi. Recurrence of acute iTTP is associated with persistence or reappearance of ADAMTS13 deficiency. Some patients remain in remission despite recurring or persisting severe ADAMTS13 deficiency. In a prospective 2-year observational study, we investigated VWF MM patterns and ADAMTS13 in patients with iTTP in remission and at acute episodes. Of the 83 patients with iTTP, 16 suffered 22 acute episodes whereas 67 remained in clinical remission during follow-up, including 13 with ADAMTS13 <10% and 54 with ADAMTS13 ≥10%. High -molecular weight to low-molecular weight VWF MM ratio based on sodium dodecyl sulfate-agarose gel electrophoresis was compared with ADAMTS13 activity. VWF MM ratio was significantly higher in patients in remission with <10% compared with ≥10% ADAMTS13 activity. Fourteen samples obtained from 13 to 50 days (interquartile range; median, 39) before acute iTTP onset (ADAMTS13 <10% in 9 patients and 10%-26% in 5) showed VWF MM ratios significantly higher than those from 13 patients remaining in remission with ADAMTS13 <10%. At acute iTTP onset, VWF MM ratio decreased significantly and was low in all patients despite <10% ADAMTS13. The VWF MM ratio does not depend exclusively on ADAMTS13 activity. The disappearance of high molecular weight VWF MMs resulting in low VWF MM ratio at iTTP onset may be explained by consumption of larger VWF MMs in the microcirculation. The very high VWF MM ratio preceding acute iTTP recurrence suggests that VWF processing is hampered more than in patients remaining in remission.

Enhanced in vivo blood brain barrier transcytosis of macromolecular cargo using an engineered pH-sensitive mouse transferrin receptor binding nanobody

BACKGROUND

The blood brain barrier limits entry of macromolecular diagnostic and therapeutic cargos. Blood brain barrier transcytosis via receptor mediated transport systems, such as the transferrin receptor, can be used to carry macromolecular cargos with variable efficiency. Transcytosis involves trafficking through acidified intracellular vesicles, but it is not known whether pH-dependent unbinding of transport shuttles can be used to improve blood brain barrier transport efficiency.

METHODS

A mouse transferrin receptor binding nanobody, NIH-mTfR-M1, was engineered to confer greater unbinding at pH 5.5 vs 7.4 by introducing multiple histidine mutations. The histidine mutant nanobodies were coupled to neurotensin for in vivo functional blood brain barrier transcytosis testing via central neurotensin-mediated hypothermia in wild-type mice. Multi-nanobody constructs including the mutant M1R56H, P96H, Y102H and two copies of the P2X7 receptor-binding 13A7 nanobody were produced to test proof-of-concept macromolecular cargo transport in vivo using quantitatively verified capillary depleted brain lysates and in situ histology.

RESULTS

The most effective histidine mutant, M1R56H, P96H, Y102H-neurotensin, caused > 8 °C hypothermia after 25 nmol/kg intravenous injection. Levels of the heterotrimeric construct M1R56H, P96H, Y102H-13A7-13A7 in capillary depleted brain lysates peaked at 1 h and were 60% retained at 8 h. A control construct with no brain targets was only 15% retained at 8 h. Addition of the albumin-binding Nb80 nanobody to make M1R56H, P96H, Y102H-13A7-13A7-Nb80 extended blood half-life from 21 min to 2.6 h. At 30-60 min, biotinylated M1R56H, P96H, Y102H-13A7-13A7-Nb80 was visualized in capillaries using in situ histochemistry, whereas at 2-16 h it was detected in diffuse hippocampal and cortical cellular structures. Levels of M1R56H, P96H, Y102H-13A7-13A7-Nb80 reached more than 3.5 percent injected dose/gram of brain tissue after 30 nmol/kg intravenous injection. However, higher injected concentrations did not result in higher brain levels, compatible with saturation and an apparent substrate inhibitory effect.

CONCLUSION

The pH-sensitive mouse transferrin receptor binding nanobody M1R56H, P96H, Y102H may be a useful tool for rapid and efficient modular transport of diagnostic and therapeutic macromolecular cargos across the blood brain barrier in mouse models. Additional development will be required to determine whether this nanobody-based shuttle system will be useful for imaging and fast-acting therapeutic applications.

Patient-Reported Outcome Measures in Patients with Thrombotic Thrombocytopenic Purpura: A Systematic Review of the Literature

Health-related quality of life (HRQoL) impacts of thrombotic thrombocytopenic purpura (TTP) have been captured in clinical studies using patient-reported outcome (PRO) measures (PROMs) that are validated for other diseases. However, the validity evidence to support the use of existing PROMs in patients with TTP is unknown. In a systematic review of the literature, including studies of adults and children with TTP, we assessed the validity evidence for use of PROMs in clinical research and clinical practice, characterized HRQoL, described the integration of PROMs in clinical practice and evaluated PRO scores for patients with TTP compared with reference populations. From an initial 4518 studies, we identified 14 studies using 16 PROMs to assess general HRQoL domains in patients in remission. No identified studies assessed the validity of PROMs for the context of use of TTP and no studies described PROM integration into TTP clinical practice or evaluated PROMs that were specific for patients with TTP. Moreover, PRO scores were worse in patients with TTP compared with reference populations and other chronic conditions. We conclude that, in patients with TTP, PROMs pick up on important patient experiences not captured by clinical outcomes at present. There is, therefore, a need for studies that assess the validity of existing PROMs in patients with TTP to determine if TTP-specific PROMs specific to patients with TTP should be developed.

Effectiveness and safety of caplacizumab in acquired thrombotic thrombocytopenic purpura: health technology assessment and classification according to the methodology established in Colombia

OBJECTIVES

Acquired thrombotic thrombocytopenic purpura (aTTP) is a rare hematological disease whose clinical management includes caplacizumab along with plasma exchange and immunosuppression, according to international guidelines. Caplacizumab has been available in Colombia since 2022. This study seeks to determine the therapeutic classification of caplacizumab according to the methodology of the Instituto de Evaluación Tecnológica en Salud.

METHODS

The classification was carried out through a deliberative process following the modified Delphi technique, with a panel of experts, made up of four hemato-oncologists, a pharmaceutical chemist, and a patient. The results of effectiveness and safety obtained through a systematic review, therapeutic thresholds (clinical significance), and degree of acceptability (willingness to use the technology) were used for the classification.

RESULTS

Fourteen effectiveness and safety outcomes were submitted for the classification process. Caplacizumab showed clinical significance for some effectiveness outcomes, was not considered inferior in terms of safety, and displayed acceptability of use. Through consensus, the panel determined that caplacizumab plus the standard regimen is superior to the standard regimen in terms of treatment response and composite outcome, and no different for the other effectiveness and safety outcomes. Likewise, in overall terms, the panel determined that caplacizumab together with the standard regimen is superior to the standard regimen.

CONCLUSION

Treatment with caplacizumab together with the standard regimen was considered superior to the standard regimen for the treatment of patients with aTTP, as it showed clinically significant benefits in critical outcomes for decision making, and a safety profile no different to its comparator.

Enhanced in Vivo Blood Brain Barrier Transcytosis of Macromolecular Cargo Using an Engineered pH-sensitive Mouse Transferrin Receptor Binding Nanobody

Background

The blood brain barrier limits entry of macromolecular diagnostic and therapeutic cargos. Blood brain barrier transcytosis via receptor mediated transport systems, such as the transferrin receptor, can be used to carry macromolecular cargos with variable efficiency. Transcytosis involves trafficking through acidified intracellular vesicles, but it is not known whether pH-dependent unbinding of transport shuttles can be used to improve blood brain barrier transport efficiency.

Methods

A mouse transferrin receptor binding nanobody, NIH-mTfR-M1, was engineered to confer greater unbinding at pH 5.5 vs 7.4 by introducing multiple histidine mutations. The histidine mutant nanobodies were coupled to neurotensin for in vivo functional blood brain barrier transcytosis testing via central neurotensin-mediated hypothermia in wild-type mice. Multi-nanobody constructs including the mutant M1 R56H, P96H, Y102H and two copies of the P2X7 receptor-binding 13A7 nanobody were produced to test proof-of-concept macromolecular cargo transport in vivo using quantitatively verified capillary depleted brain lysates and in situ histology.

Results

The most effective histidine mutant, M1 R56H, P96H, Y102H -neurotensin, caused >8°C hypothermia after 25 nmol/kg intravenous injection. Levels of the heterotrimeric construct M1 56,96,102His -13A7-13A7 in capillary depleted brain lysates peaked at 1 hour and were 60% retained at 8 hours. A control construct with no brain targets was only 15% retained at 8 hours. Addition of the albumin-binding Nb80 nanobody to make M1 R56H, P96H, Y102H -13A7-13A7-Nb80 extended blood half-life from 21 minutes to 2.6 hours. At 30-60 minutes, biotinylated M1 R56H, P96H, Y102H -13A7-13A7-Nb80 was visualized in capillaries using in situ histochemistry, whereas at 2-16 hours it was detected in diffuse hippocampal and cortical cellular structures. Levels of M1 R56H, P96H, Y102H -13A7-13A7-Nb80 reached more than 3.5 percent injected dose/gram of brain tissue after 30 nmol/kg intravenous injection. However, higher injected concentrations did not result in higher brain levels, compatible with saturation and an apparent substrate inhibitory effect.

Conclusion

The pH-sensitive mouse transferrin receptor binding nanobody M1 R56H, P96H, Y102H may be a useful tool for rapid and efficient modular transport of diagnostic and therapeutic macromolecular cargos across the blood brain barrier in mouse models. Additional development will be required to determine whether this nanobody-based shuttle system will be useful for imaging and fast-acting therapeutic applications.

Long-term follow-up of patients treated with caplacizumab and safety and efficacy of repeat caplacizumab use: Post-HERCULES study

INTRODUCTION

Caplacizumab demonstrated efficacy and safety in patients with immune-mediated thrombotic thrombocytopenic purpura (iTTP) in the phase 3 HERCULES trial. However, data on long-term outcomes following caplacizumab treatment are limited.

OBJECTIVES

The post-HERCULES trial (NCT02878603) evaluated long-term outcomes of patients with iTTP treated with caplacizumab in HERCULES and safety and efficacy of repeated caplacizumab use.

PATIENTS/METHODS

Over 3 years of follow-up, patients could receive open-label caplacizumab with therapeutic plasma exchange (TPE) and immunosuppressive therapy (IST) in case of recurrence. Adverse events (AEs) were assessed during the overall study period (intention-to-observe [ITO] population) and during recurrences (recurrence population). TTP-related events (TTP-related death, recurrence, major thromboembolic events) were assessed in the efficacy ITO population (patients without recurrence during HERCULES or before post-HERCULES).

RESULTS

Among 104 enrolled patients, incidences of AEs and serious AEs were similar between patients who had received caplacizumab + TPE + IST during HERCULES (n = 75) and those treated with placebo + TPE + IST (placebo; n = 29). TTP-related events occurred in 8% of patients (4/49) randomized to caplacizumab during HERCULES versus 38% (11/29) randomized to placebo. Nineteen patients had ≥1 recurrence; 13 of these were treated with caplacizumab. The first recurrence episode was resolved or resolving for all patients treated with caplacizumab, including nine patients with repeat caplacizumab use. All second recurrences (6/6) were resolved. Safety profile of caplacizumab for treatment of recurrence was consistent with HERCULES; most bleeding events were nonserious. No major cases of organ dysfunction were observed.

CONCLUSIONS

Long-term follow-up supports the safety and efficacy of caplacizumab for iTTP and its repeated use for recurrences.