Diligent Design Enables Antibody-ASO Conjugates with Optimal Pharmacokinetic Properties

Antisense-oligonucleotides (ASOs) are a promising drug modality for the treatment of neurological disorders, but the currently established route of administration via intrathecal delivery is a major limitation to its broader clinical application. An attractive alternative is the conjugation of the ASO to an antibody that facilitates access to the central nervous system (CNS) after peripheral application and target engagement at the blood-brain barrier, followed by transcytosis. Here, we show that the diligent conjugate design of Brainshuttle-ASO conjugates is the key to generating promising delivery vehicles and thereby establishing design principles to create optimized molecules with drug-like properties. An innovative site-specific transglutaminase-based conjugation technology was chosen and optimized in a stepwise process to identify the best-suited conjugation site, tags, reaction conditions, and linker design. The overall conjugation performance was found to be specifically governed by the choice of buffer conditions and the structure of the linker. The combination of the peptide tags YRYRQ and RYESK was chosen, showing high conjugation fidelity. Elaborate conjugate analysis revealed that one leading differentiating factor was hydrophobicity. The increase of hydrophobicity by the ASO payload could be mitigated by the appropriate choice of conjugation site and the heavy chain position 297 proved to be the most optimal. Evaluating the properties of the linker suggested a short bicyclo[6.1.0]nonyne (BCN) unit as best suited with regards to conjugation performance and potency. Promising in vitro activity and in vivo pharmacokinetic behavior of optimized Brainshuttle-ASO conjugates, based on a microtubule-associated protein tau (MAPT) targeting oligonucleotide, suggest that such designs have the potential to serve as a blueprint for peripherally delivered ASO-based drugs for the CNS in the future.

Vitamin D deficiency and vitamin D receptor FokI polymorphism as risk factors for COVID-19

BACKGROUND

Given the sparse data on vitamin D status in pediatric COVID-19, we investigated whether vitamin D deficiency could be a risk factor for susceptibility to COVID-19 in Egyptian children and adolescents. We also investigated whether vitamin D receptor (VDR) FokI polymorphism could be a genetic marker for COVID-19 susceptibility.

METHODS

One hundred and eighty patients diagnosed to have COVID-19 and 200 matched control children and adolescents were recruited. Patients were laboratory confirmed as SARS-CoV-2 positive by real-time RT-PCR. All participants were genotyped for VDR Fok1 polymorphism by RT-PCR. Vitamin D status was defined as sufficient for serum 25(OH) D at least 30 ng/mL, insufficient at 21-29 ng/mL, deficient at <20 ng/mL.

RESULTS

Ninety-four patients (52%) had low vitamin D levels with 74 (41%) being deficient and 20 (11%) had vitamin D insufficiency. Vitamin D deficiency was associated with 2.6-fold increased risk for COVID-19 (OR = 2.6; [95% CI 1.96-4.9]; P = 0.002. The FokI FF genotype was significantly more represented in patients compared to control group (OR = 4.05; [95% CI: 1.95-8.55]; P < 0.001).

CONCLUSIONS

Vitamin D deficiency and VDR Fok I polymorphism may constitute independent risk factors for susceptibility to COVID-19 in Egyptian children and adolescents.

IMPACT

Vitamin D deficiency could be a modifiable risk factor for COVID-19 in children and adolescents because of its immune-modulatory action. To our knowledge, ours is the first such study to investigate the VDR Fok I polymorphism in Caucasian children and adolescents with COVID-19. Vitamin D deficiency and the VDR Fok I polymorphism may constitute independent risk factors for susceptibility to COVID-19 in Egyptian children and adolescents. Clinical trials should be urgently conducted to test for causality and to evaluate the efficacy of vitamin D supplementation for prophylaxis and treatment of COVID-19 taking into account the VDR polymorphisms.

Cytokine profile in Egyptian children and adolescents with COVID-19 pneumonia: A multicenter study

BACKGROUND

To date, the cytokine profile in children and adolescent with novel coronavirus disease 2019 (COVID-19) has not been reported.

OBJECTIVES

We investigated serum levels of a panel of key cytokines in children and adolescent with COVID-19 pneumonia with a primary focus on "cytokine storm" cytokines such as interleukin (IL)-1β, IL-6, IL-17, IL-2, IL-4, IL-10, interferon (IFN-γ), tumor necrosis factor (TNF)-α, and two chemokines interferon-inducible protein-10 (IP-10) and IL-8. We also studied whether these cytokines could be potential markers for illness severity in COVID-19 pneumonia.

METHODS

Ninety-two symptomatic patients aged less than 18 years with confirmed COVID-19 pneumonia and 100 well-matched healthy controls were included in this multi-center study. For all patients, the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in respiratory fluid specimens was detected by real-time reverse-transcriptase polymerase chain reaction. We measured serum concentrations of studied cytokines by using flow cytometry.

RESULTS

Patients with COVID-19 had significantly higher median IL-1β, IL-6, IL-8, IL-10, IL-17, TNF-α, and IP-10 serum levels than did control children (all p < 0.01). Patients with severe COVID-19 pneumonia had significantly higher median IL-1β, IL-6, and IP-10 serum levels as compared with those with moderate COVID-19 pneumonia; all p < 0.01. ROC analysis revealed that three of the studied markers (IL-6, IL-1β, and IP-10) could predict severe COVID-19 pneumonia cases with the largest AUC for IL-6 of 0.893 (95% confidence interval: 0.84-0.98; p < 0.01).

CONCLUSION

Our study shows that pediatric patients with COVID-19 pneumonia have markedly elevated serum IL-1β, IL-6, IL-8, IL-10, IL-17, TNF-α, and IP-10 levels at the initial phase of the illness indicating a cytokine storm following SARS-CoV-2 infection. Moreover, serum IL-6, IL-1β, and IP-10 concentrations were independent predictors for severe COVID-19 pneumonia.