A class II MHC-targeted vaccine elicits immunity against SARS-CoV-2 and its variants.

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in over 100 million infections and millions of deaths. Effective vaccines remain the best hope of curtailing SARS-CoV-2 transmission, morbidity, and mortality. The vaccines in current use require cold storage and sophisticated manufacturing capacity, which complicates their distribution, especially in less developed countries. We report the development of a candidate SARS-CoV-2 vaccine that is purely protein based and directly targets antigen-presenting cells. It consists of the SARS-CoV-2 Spike receptor-binding domain (SpikeRBD) fused to an alpaca-derived nanobody that recognizes class II major histocompatibility complex antigens (VHHMHCII). This vaccine elicits robust humoral and cellular immunity against SARS-CoV-2 and its variants. Both young and aged mice immunized with two doses of VHHMHCII-SpikeRBD elicit high-titer binding and neutralizing antibodies. Immunization also induces strong cellular immunity, including a robust CD8 T cell response. VHHMHCII-SpikeRBD is stable for at least 7 d at room temperature and can be lyophilized without loss of efficacy.

Nasal delivery of single-domain antibody improves symptoms of SARS-CoV-2 infection in an animal model.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes the disease COVID-19 can lead to serious symptoms, such as severe pneumonia, in the elderly and those with underlying medical conditions. While vaccines are now available, they do not work for everyone and therapeutic drugs are still needed, particularly for treating life-threatening conditions. Here, we showed nasal delivery of a new, unmodified camelid single-domain antibody (VHH), termed K-874A, effectively inhibited SARS-CoV-2 titers in infected lungs of Syrian hamsters without causing weight loss and cytokine induction. In vitro studies demonstrated that K-874A neutralized SARS-CoV-2 in both VeroE6/TMPRSS2 and human lung-derived alveolar organoid cells. Unlike other drug candidates, K-874A blocks viral membrane fusion rather than viral attachment. Cryo-electron microscopy revealed K-874A bound between the receptor binding domain and N-terminal domain of the virus S protein. Further, infected cells treated with K-874A produced fewer virus progeny that were less infective. We propose that direct administration of K-874A to the lung could be a new treatment for preventing the reinfection of amplified virus in COVID-19 patients.

IL17A/F nanobody sonelokimab in patients with plaque psoriasis: a multicentre, randomised, placebo-controlled, phase 2b study.

BACKGROUND: Sonelokimab (also known as M1095) is a novel trivalent nanobody comprised of monovalent camelid-derived (ie, from the Camelidae family of mammals, such as camels, llamas, and alpacas) nanobodies specific to human interleukin (IL)-17A, IL-17F, and human serum albumin. Nanobodies are a novel class of proprietary therapeutic proteins based on single-domain, camelid, heavy-chain-only antibodies. We assessed the efficacy, safety, and tolerability of sonelokimab across four dosage regimens compared with placebo in patients with plaque-type psoriasis. Secukinumab served as an active control. METHODS: This multicentre, randomised, placebo-controlled, phase 2b trial was done at 41 clinics and research sites in Bulgaria, Canada, Czech Republic, Germany, Hungary, Poland, and the USA. Participants (aged 18-75 years) with stable moderate to severe plaque-type psoriasis (defined as an Investigator's Global Assessment [IGA] score of ≥3, a body surface area involvement of ≥10%, and a Psoriasis Area and Severity Index score of ≥12) for more than 6 months before randomisation, who were candidates for systemic biological therapy were included. Participants previously treated with more than two biologics or any therapy targeting IL-17 were excluded. Randomisation was stratified by weight (≤90 kg or >90 kg) and previous use of biologics. Investigators, participants, and vendors remained masked for the duration of the study, with the exception of each site's study drug administrator (who did not complete any other assessments in the study) and a study monitor who only assessed drug preparation, administration, and accountability. The study sponsor remained masked until all week 24 data were clean and locked. Participants were randomly assigned (1:1:1:1:1:1) using a centralised interactive response technology system to one of six parallel treatment groups: placebo group, sonelokimab 30 mg group, sonelokimab 60 mg group, sonelokimab 120 mg normal load group, sonelokimab 120 mg augmented load group, or secukinumab 300 mg group. All participants underwent a 4-week screening period, a 12-week placebo-controlled induction period, a 12-week dose maintenance or escalation period, and a 24-week response assessment or dose-holding period. During the placebo-controlled induction period (weeks 0-12), participants received either placebo (at weeks 0, 1, 2, 3, 4, 6, 8, and 10), sonelokimab 30 mg, 60 mg, or 120 mg normal load (at weeks 0, 2, 4, and 8), sonelokimab 120 mg augmented load (at weeks 0, 2, 4, 6, 8, and 10), or secukinumab 300 mg (at weeks 0, 1, 2, 3, 4, and 8), with placebo given at weeks 1, 3, 6, and 10 in the sonelokimab 30 mg, 60 mg, and 120 mg normal load groups, at weeks 1 and 3 in the sonelokimab 120 mg augmented load group, and at weeks 6 and 10 in the secukinumab 300 mg group. During the dose maintenance or escalation period (weeks 12-24), participants assigned to the placebo group received sonelokimab 120 mg (at weeks 12, 14, 16, and then every 4 weeks); those assigned to sonelokimab 30 mg or 60 mg groups with an IGA score of more than 1 were escalated to 120 mg and then every 4 weeks, and those with an IGA score of 1 or less stayed on the assigned dose at week 12 and then every 4 weeks; those assigned to the sonelokimab 120 mg groups received sonelokimab 120 mg at week 12 and then every 8 weeks (normal load group) or every 4 weeks (augmented load); and those assigned to the secukinumab 300 mg group received secukinumab 300 mg at week 12 and then every 4 weeks. During this period, placebo was given at week 14 in all groups, except in participants who initially received placebo, and at week 16 in the sonelokimab 120 mg normal load group. In the response assessment with dose-holding period (weeks 24-48), participants in the sonelokimab 30 mg or 60 mg groups who had dose escalation to 120 mg remained on the same regimen regardless of the IGA score at week 24. Participants in the secukinumab 300 mg group also remained on the same regimen regardless of IGA score at week 24. Participants in the sonelokimab 30 mg and 60 mg groups without dose escalation, and all participants in the two sonelokimab 120 mg groups (including placebo rollover patients) were eligible to stop the study drug at week 24. Those participants with an IGA score of 0 at week 24 received placebo; these participants resumed the previous dose of sonelokimab every 4 weeks when they had an IGA score of 1 or more (assessed every 4 weeks). Participants in these groups with an IGA score of 1 or more at week 24 continued on the same dosage. All study treatments were administered as subcutaneous injections. The final dose in all groups was given at week 44. The primary outcome was the proportion of participants in the sonelokimab groups with an IGA of clear or almost clear (score 0 or 1) at week 12 compared with the placebo group. The primary outcome and safety outcomes were assessed on an intention-to-treat basis. The study was not powered for formal comparisons between sonelokimab and secukinumab groups. This trial is registered with ClinicalTrials.gov, NCT03384745. FINDINGS: Between Aug 15, 2018, and March 27, 2019, 383 patients were assessed for eligibility, 313 of whom were enrolled and randomly assigned to the placebo group (n=52), the sonelokimab 30 mg group (n=52), the sonelokimab 60 mg group (n=52), the sonelokimab 120 mg normal load group (n=53), the sonelokimab 120 mg augmented load group (n=51), or the secukinumab 300 mg group (n=53). Baseline characteristics of participants were similar among the groups. At week 12, none (0·0% [95% CI 0·0-6·8]) of the 52 participants in the placebo group had an IGA score of 0 or 1 versus 25 (48·1% [34·0-62·4], p<0·0001) of 52 participants in the sonelokimab 30 mg group, 44 (84·6% [71·9-93·1], p<0·0001) of 52 participants in the sonelokimab 60 mg group, 41 (77·4% [63·8-87·7], p<0·0001) of 53 participants in the sonelokimab 120 mg normal load group, 45 (88·2% [76·1-95·6], p<0·0001) of 51 participants in the sonelokimab 120 mg augmented load group, and 41 (77·4% [63·8-87·7], p<0·0001) of 53 participants in the secukinumab 300 mg group. During the placebo-controlled induction period, 155 (49·5%) of 313 participants had one or more mostly mild to moderate adverse event; the most frequent adverse events in all participants on sonelokimab during weeks 0-12 were nasopharyngitis (28 [13·5%] of 208 participants), pruritus (14 [6·7%] participants), and upper respiratory tract infection (nine [4·3%] participants). One patient from all sonelokimab-containing groups had Crohn's disease that developed during weeks 12-52. Over 52 weeks, sonelokimab safety was similar to secukinumab, with the possible exception of manageable Candida infections (one [1·9%] of 53 participants in the secukinumab group had a Candida infection vs 19 [7·4%] of 257 participants in all sonelokimab-containing groups). INTERPRETATION: Treatment with sonelokimab doses of 120 mg or less showed significant clinical benefit over placebo, with rapid onset of treatment effect, durable improvements, and an acceptable safety profile. FUNDING: Avillion.

Effectiveness of Caplacizumab Nanobody in Acquired Thrombotic Thrombocytopenic Purpura Refractory to Conventional Treatment.

Acquired thrombocytopenic thrombotic purpura (aTTP) is an autoantibody-mediated disease against the enzyme A Disintegrin and Metalloprotease domain with ThromboSpondin-1 type motif 13, which until now has been treated with plasma exchange (PEX) and corticosteroids. A 29-year-old female patient, who presented with aTTP in the context of pregnancy, has developed multiple relapses after treatment with PEX, corticosteroids, and rituximab. Recently, caplacizumab, a nanobody against von Willebrand factor, has been approved for the treatment of aTTP. In our patient, caplacizumab achieved better disease control, with a lower platelet count restoration time, days of PEX and hospitalization duration, as compared to standard therapy, reproducing the results of clinical trials. Caplacizumab represents a significant advance in the treatment of aTTP, especially in cases of recurrent relapses.

Immuno-PET imaging of 68Ga-labeled nanobody Nb109 for dynamic monitoring the PD-L1 expression in cancers.

The checkpoint blockade immunotherapy has become a potent treatment strategy for cancers, and programmed death ligand-1 (PD-L1) is a prominent checkpoint ligand that is highly expressed in some cancers. The identification of immune checkpoint marker PD-L1 is critical for improving the success of immunotherapy. Accordingly, the binding specificity and dynamic monitoring property of a non-blocking nanobody tracer 68Ga-NOTA-Nb109 to PD-L1 were assessed in this study. The endogenous expression level of PD-L1 in several cancer cells was measured by flow cytometry, Western blot, and cellular uptake assay. Sensitivity and specificity of 68Ga-NOTA-Nb109 in monitoring the expression of PD-L1 in vivo were evaluated by PET imaging of different tumor-bearing models (U87, high PD-L1 expression; HCT 116, medium PD-L1 expression; and NCI-H1299, low PD-L1 expression). In vivo PET imaging results agreed well with those detected in vitro. In addition, PET imaging of PD-L1 expression in U87 and NCI-H1299 xenografts using 18F-FDG was also performed for comparison. The maximum tumor-to-muscle uptake ratio of 68Ga-NOTA-Nb109 was more than twofold that of 18F-FDG in U87 xenograft. The change of PD-L1 expression in NCI-H1299 cells and xenografts induced by cisplatin (CDDP) was sensitively monitored by 68Ga-NOTA-Nb109. This study demonstrated the feasibility of tracer 68Ga-NOTA-Nb109 for specifically targeting endogenous PD-L1 and dynamic monitoring the change of PD-L1 expression, and could guide the immunotherapy and immunochemotherapy for refractory cancers.

Development of a 99mTc-Labeled Single-Domain Antibody for SPECT/CT Assessment of HER2 Expression in Breast Cancer.

Accurate determination of human epidermal growth factor receptor 2 (HER2) expression is essential for HER2-targeted therapy in patients with cancer. HER2 expression in a complex environment, such as in a heterogeneous tumor, makes the precise assessment of the HER2 status difficult using current methods. In this study, we developed a novel 99mTc-labeled anti-HER2 single-domain antibody (99mTc-NM-02) as a molecular imaging tracer for the noninvasive detection of HER2 expression and investigated its safety, radiation dosimetry, biodistribution, and tumor-targeting potential in 10 patients with breast cancer. Our data showed that no drug-related adverse reactions occurred. The tracer mainly accumulated in the kidneys and liver with mild uptake in the spleen, intestines, and thyroid; however, only background tracer levels were observed in other organs where primary tumors and metastases typically occurred. The mean effective dose was 6.56 × 10-3 mSv/MBq, and tracer uptake was visually observed in the primary tumors and metastases. A maximal standard uptake value of 1.5 was determined as a reasonable cutoff for identifying HER2 positivity using SPECT/CT imaging. Our 99mTc-NM-02 tracer is safe for use in breast cancer imaging, with reasonable radiation doses, favorable biodistribution, and imaging characteristics. 99mTc-NM-02 SPECT imaging may be an accurate and noninvasive method to detect the HER2 status in patients with breast cancer.

A case of thrombotic thrombocytopenic purpura associated with COVID-19.

Acquired thrombotic thrombocytopenic purpura (TTP) is an autoimmune disease that can be triggered by different events, including viral infections. It presents as thrombotic microangiopathy and can lead to severe complications that often require management in the intensive care unit (ICU). We report a patient who presented with acquired TTP following COVID-19 infection. A 44-year-old woman presented to the emergency department with severe anemia, acute kidney injury and respiratory failure due to COVID-19. Clinical and laboratory findings were suggestive for thrombotic microangiopathy. On day 8 laboratory tests confirmed the diagnosis of acquired TTP. The patient needed 14 plasma exchanges, treatment with steroids, rituximab and caplacizumab and 18 days of mechanical ventilation. She completely recovered and was discharged home on day 51. Acquired TTP can be triggered by different events leading to immune stimulation. COVID-19 has been associated with different inflammatory and auto-immune diseases. Considering the temporal sequence and the lack of other possible causes, we suggest that COVID-19 infection could have been the triggering factor in the development of TTP. Since other similar cases have already been described, possible association between COVID and TTP deserves further investigation.

Inhibition of neovascularisation in human endothelial cells using anti NRP-1 nanobody fused to truncated form of diphtheria toxin as a novel immunotoxin.

Neuropilin-1 (NRP-1) regulates a range of physiological and pathological processes, including angiogenesis. Targeting of NRP1 is considered a significant approach in cancer therapy. In the present study, a novel antiNRP1 immunotoxin (αNRP1 IT) was developed by genetic fusion of a single domain (VHH) anti-NRP-1 antibody fragment to a truncated diphtheria toxin. The αNRP1 IT was expressed into bacterial cells as an inclusion body (IB). Expression of αNRP1 IT was confirmed by SDS-PAGE and western blotting. Recombinant αNRP1 IT was purified using nickel affinity chromatography. Toxicity and antiangiogenesis effect of αNRP1 IT was investigated both in vitro and in vivo. Results showed that αNRP1 IT significantly reduced the viability of human umbilical vein endothelial cell line (HUVEC) (p < .05). The αNRP1 IT significantly inhibited tube formation of HUVEC cells (p < .001). Furthermore, αNRP1 IT inhibited angiogenesis in Chick Chorioallantoic Membrane (CAM) Assay. These data suggest the potential of αNRP1 IT as a novel therapeutic in targeted cancer therapy.

Pharmacokinetics of Single Domain Antibodies and Conjugated Nanoparticles Using a Hybrid near Infrared Method.

Iron oxide nanoparticles and single domain antibodies from camelids (VHHs) have been increasingly recognized for their potential uses for medical diagnosis and treatment. However, there have been relatively few detailed characterizations of their pharmacokinetics (PK). The aim of this study was to develop imaging methods and pharmacokinetic models to aid the future development of a novel family of brain MRI molecular contrast agents. An efficient near-infrared (NIR) imaging method was established to monitor VHH and VHH conjugated nanoparticle kinetics in mice using a hybrid approach: kinetics in blood were assessed by direct sampling, and kinetics in kidney, liver, and brain were assessed by serial in vivo NIR imaging. These studies were performed under "basal" circumstances in which the VHH constructs and VHH-conjugated nanoparticles do not substantially interact with targets nor cross the blood brain barrier. Using this approach, we constructed a five-compartment PK model that fits the data well for single VHHs, engineered VHH trimers, and iron oxide nanoparticles conjugated to VHH trimers. The establishment of the feasibility of these methods lays a foundation for future PK studies of candidate brain MRI molecular contrast agents.

Caplacizumab for treatment of thrombotic thrombocytopenic purpura in a patient with anaphylaxis to fresh-frozen plasma.

BACKGROUND: Plasma exchange with plasma replacement has been the mainstay for the treatment of thrombotic thrombocytopenic purpura (TTP) for several decades. Recently an anti-von Willebrand factor (VWF) medication, caplacizumab, has been approved for treatment of TTP when used with plasma exchange. We report a patient with immune-mediated TTP that had an anaphylactic reaction to plasma who was then given caplacizumab daily for 1 week without further plasma exchange therapy with a good clinical and laboratory response. CASE REPORT: A 63-year-old woman with acute confusion and multiple ecchymoses after tooth extraction developed TTP with a hemoglobin (Hb) of 6.3 g/dL, white blood cell count 15 × 109 /L, platelets (PLTs) 12 × 109 /L, lactate dehydrogenase (LDH) 1212 IU/mL, and creatinine 0.9 mg/dL. Her ADAMTS13 level was less than 5% and plasma exchange was started. During the first plasma exchange the patient developed anaphylaxis with hypotension, shortness of breath, angioedema, and urticaria. She recovered from this reaction with treatment and no further plasma exchanges were performed. Instead she was given methylprednisolone, caplacizumab, and later rituximab. The caplacizumab was given daily for 8 days during which her PLT counts and ADAMTS13 levels improved. Her Hb level also increased. She continued to receive oral prednisone and rituximab after discharge was doing well latest follow up (Day 114). CONCLUSION: Caplacizumab may be used safely and effectively without concomitant plasma exchange in a patient with anaphylaxis to plasma.

Role of caplacizumab in the treatment of acquired thrombotic thrombocytopenic purpura.

Acquired thrombotic thrombocytopenic purpura is a rare blood disorder with a high early mortality rate, if untreated. Standard of care plasma exchange and glucocorticoids have dramatically improved survival. However, additional advancements are necessary to further decrease mortality. Caplacizumab-yhdp (Cablivi®) is the first Food and Drug Administration-approved treatment indicated for adult patients with acquired thrombotic thrombocytopenic purpura, in combination with plasma exchange and immunosuppressive therapy. However, there are considerable risks associated with the use of caplacizumab and they must be weighed against the benefits of the medication.

A genetically encoded toolkit of functionalized nanobodies against fluorescent proteins for visualizing and manipulating intracellular signalling.

BACKGROUND: Intrabodies enable targeting of proteins in live cells, but generating specific intrabodies against the thousands of proteins in a proteome poses a challenge. We leverage the widespread availability of fluorescently labelled proteins to visualize and manipulate intracellular signalling pathways in live cells by using nanobodies targeting fluorescent protein tags. RESULTS: We generated a toolkit of plasmids encoding nanobodies against red and green fluorescent proteins (RFP and GFP variants), fused to functional modules. These include fluorescent sensors for visualization of Ca2+, H+ and ATP/ADP dynamics; oligomerising or heterodimerising modules that allow recruitment or sequestration of proteins and identification of membrane contact sites between organelles; SNAP tags that allow labelling with fluorescent dyes and targeted chromophore-assisted light inactivation; and nanobodies targeted to lumenal sub-compartments of the secretory pathway. We also developed two methods for crosslinking tagged proteins: a dimeric nanobody, and RFP-targeting and GFP-targeting nanobodies fused to complementary hetero-dimerizing domains. We show various applications of the toolkit and demonstrate, for example, that IP3 receptors deliver Ca2+ to the outer membrane of only a subset of mitochondria and that only one or two sites on a mitochondrion form membrane contacts with the plasma membrane. CONCLUSIONS: This toolkit greatly expands the utility of intrabodies and will enable a range of approaches for studying and manipulating cell signalling in live cells.

Antibodies Targeting Chemokine Receptors CXCR4 and ACKR3.

Dysregulation of the chemokine system is implicated in a number of autoimmune and inflammatory diseases, as well as cancer. Modulation of chemokine receptor function is a very promising approach for therapeutic intervention. Despite interest from academic groups and pharmaceutical companies, there are currently few approved medicines targeting chemokine receptors. Monoclonal antibodies (mAbs) and antibody-based molecules have been successfully applied in the clinical therapy of cancer and represent a potential new class of therapeutics targeting chemokine receptors belonging to the class of G protein-coupled receptors (GPCRs). Besides conventional mAbs, single-domain antibodies and antibody scaffolds are also gaining attention as promising therapeutics. In this review, we provide an extensive overview of mAbs, single-domain antibodies, and other antibody fragments targeting CXCR4 and ACKR3, formerly referred to as CXCR7. We discuss their unique properties and advantages over small-molecule compounds, and also refer to the molecules in preclinical and clinical development. We focus on single-domain antibodies and scaffolds and their utilization in GPCR research. Additionally, structural analysis of antibody binding to CXCR4 is discussed. SIGNIFICANCE STATEMENT: Modulating the function of GPCRs, and particularly chemokine receptors, draws high interest. A comprehensive review is provided for monoclonal antibodies, antibody fragments, and variants directed at CXCR4 and ACKR3. Their advantageous functional properties, versatile applications as research tools, and use in the clinic are discussed.

CD38 produces nicotinic acid adenosine dinucleotide phosphate in the lysosome.

Nicotinic acid adenosine dinucleotide phosphate (NAADP) is a Ca2+-mobilizing second messenger that regulates a wide range of biological activities. However, the mechanism of its biogenesis remains controversial. CD38 is the only enzyme known to catalyze NAADP synthesis from NADP and nicotinic acid. CD38-mediated catalysis requires an acidic pH, suggesting that NAADP may be produced in acidic endolysosomes, but this hypothesis is untested. In this study, using human cell lines, we specifically directed CD38 to the endolysosomal system and assessed cellular NAADP production. First, we found that nanobodies targeting various epitopes on the C-terminal domain of CD38 could bind to cell surface-localized CD38 and induce its endocytosis. We also found that CD38 internalization occurred via a clathrin-dependent pathway, delivered CD38 to the endolysosome, and elevated intracellular NAADP levels. We also created a CD38 variant for lysosome-specific expression, which not only withstood the degradative environment in the lysosome, but was also much more active than WT CD38 in elevating cellular NAADP levels. Supplementing CD38-expressing cells with nicotinic acid substantially increased cellular NAADP levels. These results demonstrate that endolysosomal CD38 can produce NAADP in human cells. They further suggest that CD38's compartmentalization to the lysosome may allow for its regulation via substrate access, rather than enzyme activation, thereby providing a reliable mechanism for regulating cellular NAADP production.

AAV9 delivered bispecific nanobody attenuates amyloid burden in the gelsolin amyloidosis mouse model.

Gelsolin amyloidosis is a dominantly inherited, incurable type of amyloidosis. A single point mutation in the gelsolin gene (G654A is most common) results in the loss of a Ca2+ binding site in the second gelsolin domain. Consequently, this domain partly unfolds and exposes an otherwise buried furin cleavage site at the surface. During secretion of mutant plasma gelsolin consecutive cleavage by furin and MT1-MMP results in the production of 8 and 5 kDa amyloidogenic peptides. Nanobodies that are able to (partly) inhibit furin or MT1-MMP proteolysis have previously been reported. In this study, the nanobodies have been combined into a single bispecific format able to simultaneously shield mutant plasma gelsolin from intracellular furin and extracellular MT1-MMP activity. We report the successful in vivo expression of this bispecific nanobody following adeno-associated virus serotype 9 gene therapy in gelsolin amyloidosis mice. Using SPECT/CT and immunohistochemistry, a reduction in gelsolin amyloid burden was detected which translated into improved muscle contractile properties. We conclude that a nanobody-based gene therapy using adeno-associated viruses shows great potential as a novel strategy in gelsolin amyloidosis and potentially other amyloid diseases.

Labeling of Anti-HER2 Nanobodies with Astatine-211: Optimization and the Effect of Different Coupling Reagents on Their in Vivo Behavior.

The use of nanobodies (Nbs) as vehicles in targeted alpha therapy (TAT) has gained great interest because of their excellent properties. They combine high in vivo affinity and specificity of binding with fast kinetics. This research investigates a novel targeted therapy that combines the α-particle emitter astatine-211 (211At) and the anti-HER2 Nb 2Rs15d to selectively target HER2+ cancer cells. Two distinctive radiochemical methodologies are investigated using three different coupling reagents. The first method uses the coupling reagents, N-succinimidyl 4-(1,2-bis-tert-butoxycarbonyl)guanidinomethyl-3-(trimethylstannyl)benzoate (Boc2-SGMTB) and N-succinimidyl-3-(trimethylstannyl)benzoate (m-MeATE), which are both directed to amino groups on the Nb, resulting in random conjugation. The second method aims at obtaining a homogeneous tracer population, via a site-specific conjugation of the N-[2-(maleimido)ethyl]-3-(trimethylstannyl)benzamide (MSB) reagent onto the carboxyl-terminal cysteine of the Nb. The resulting radioconjugates are evaluated in vitro and in vivo. 2Rs15d is labeled with 211At using Boc2-SGMTB, m-MeATE, and MSB. After astatination and purification, the binding specificity of the radioconjugates is validated on HER2+ cells, followed by an in vivo biodistribution assessment in SKOV-3 xenografted mice. α-camera imaging is performed to determine uptake and activity distribution in kidneys/tumors. 2Rs15d astatination resulted in a high radiochemical purity >95% for all radioconjugates. The biodistribution studies of all radioconjugates revealed comparable tumor uptake (higher than 8% ID/g at 1 h). [211At]SAGMB-2Rs15d showed minor uptake in normal tissues. Only in the kidneys, a higher uptake was measured after 1 h, but decreased rapidly after 3 h. Astatinated Nbs consisting of m-MeATE or MSB reagents revealed elevated uptake in lungs and stomach, indicating the presence of released 211At. α-Camera imaging of tumors revealed a homogeneous activity distribution. The radioactivity in the kidneys was initially concentrated in the renal cortex, while after 3 h most radioactivity was measured in the medulla, confirming the fast washout into urine. Changing the reagents for Nb astatination resulted in different in vivo biodistribution profiles, while keeping the targeting moiety identical. Boc2-SGMTB is the preferred reagent for Nb astatination because of its high tumor uptake, its low background signals, and its fast renal excretion. We envision [211At]SAGMB-2Rs15d to be a promising therapeutic agent for TAT and aim toward efficacy evaluation.

Selective Cytotoxicity to HER2 Positive Breast Cancer Cells by Saporin-Loaded Nanobody-Targeted Polymeric Nanoparticles in Combination with Photochemical Internalization.

In cancer treatment, polymeric nanoparticles (NPs) can serve as a vehicle for the delivery of cytotoxic proteins that have intracellular targets but that lack well-defined mechanisms for cellular internalization, such as saporin. In this work, we have prepared PEGylated poly(lactic acid- co-glycolic acid- co-hydroxymethyl glycolic acid) (PLGHMGA) NPs for the selective delivery of saporin in the cytosol of HER2 positive cancer cells. This selective uptake was achieved by decorating the surface of the NPs with the 11A4 nanobody that is specific for the HER2 receptor. Confocal microscopy observations showed rapid and extensive uptake of the targeted NPs (11A4-NPs) by HER2 positive cells (SkBr3) but not by HER2 negative cells (MDA-MB-231). This selective uptake was blocked upon preincubation of the cells with an excess of nanobody. Nontargeted NPs (Cys-NPs) were not taken up by either type of cells. Importantly, a dose-dependent cytotoxic effect was only observed on SkBr3 cells when these were treated with saporin-loaded 11A4-NPs in combination with photochemical internalization (PCI), a technique that uses a photosensitizer and local light exposure to facilitate endosomal escape of entrapped nanocarriers and biomolecules. The combined use of saporin-loaded 11A4-NPs and PCI strongly inhibited cell proliferation and decreased cell viability through induction of apoptosis. Also the cytotoxic effect could be reduced by an excess of nanobody, reinforcing the selectivity of this system. These results suggest that the combination of the targeting nanobody on the NPs with PCI are effective means to achieve selective uptake and cytotoxicity of saporin-loaded NPs.

Nanobody-Targeted Photodynamic Therapy Selectively Kills Viral GPCR-Expressing Glioblastoma Cells.

Photodynamic therapy (PDT) eradicates tumors by the local activation of a photosensitizer with near-infrared light. One of the aspects hampering the clinical use of PDT is the poor selectivity of the photosensitizer. To improve this, we have recently introduced a new approach for targeted PDT by conjugating photosensitizers to nanobodies. Diverse G protein-coupled receptors (GPCRs) show aberrant overexpression in tumors and are therefore interesting targets in cancer therapy. Here we show that GPCR-targeting nanobodies can be used in targeted PDT. We have developed a nanobody binding the extracellular side of the viral GPCR US28, which is detected in tumors like glioblastoma. The nanobody was site-directionally conjugated to the water-soluble photosensitizer IRDye700DX. This nanobody-photosensitizer conjugate selectively killed US28-expressing glioblastoma cells both in 2D and 3D cultures upon illumination with near-infrared light. This is the first example employing a GPCR as target for nanobody-directed PDT. With the emerging role of GPCRs in cancer, this data provides a new angle for exploiting this large family of receptors for targeted therapies.

Caplacizumab treatment for acquired thrombotic thrombocytopenic purpura (HERCULES trial).

CLINICAL QUESTION: In people with acquired thrombotic thrombocytopenic purpura (TTP), does caplacizumab decrease the time to normalisation of the platelet count and the risk of death and complications caused by thrombotic events and organ damage? EVIDENCE FROM TRIAL: In adults with acquired TTP, caplacizumab decreased the time to normalisation of the platelet count and decreased the risk of TTP-related death and recurrence of TTP.