2. INTRODUCTION AND RATIONALE New SARS-CoV-2 specific monoclonal antibodiestherapies
From the beginning of the worldwide pandemic till now no effective specific anti-
SARS-CoV-2 treatment was available1,2. In June 2021 the use of SARS-CoV-2 monoclonal
antibodies as early treatment for SARS-CoV-2 infected individuals became available
in the Netherlands after an emergency use authorisation of the FDA and EMA. First
large phase-III randomised controlled clinical trials have showed that SARS-CoV-2
monoclonal antibodies, when given early after the onset of symptoms, bind the
SARS-CoV-2 spike protein effectively and prevent hospital admission and death3-7.
Additionally, promising SARS-CoV-2 compounds ,such as the oral antivirals
molnupiravir8 and nirmatrelvir/ritonavir paxlovid9received recently received an
emergency use authorization of the FDA in patients with Covid-19 at high risk of
hospitalization and death. EMA's human medicines committee (CHMP) has also started a
rolling review of the oral antiviral medicine molnupiravir.

Pathophysiology SARS-CoV-2 monoclonal antibodies

SARS-CoV-2 monoclonal antibodies recognize a single and unique epitope on the SARS-CoV-2
spike proteins and are derived from donor B lymphocytes. The donor B-lymphocytes can be
derived either from patients who had Covid-19 or humanized mice who were exposed to
SARS-CoV-23,10. The SARS-CoV-2 monoclonal antibodies inhibit the entry of the virus into
the host cells (neutralization). Furthermore, antibody binding results in opsonization
and is the first step of phagocytosis, eventually resulting in apoptosis and necrosis of
the infected cells3. Monoclonal antibodies can be altered artificially in the laboratory
to combat emerging variants of SARS-CoV-23. Threewo frequently investigated combinations
are casirivimab with imdevimab, sotrovimabsotrovimab and and balanivimab with
etesevimab4-7,11.

Small-molecules for Covid-19 At present, many candidate small-molecule therapeutics have
been developed that can inhibit both the infection and replication of SARS-CoV-2 and even
potentially relieve cytokine storms and other related complications. As SARS-CoV-2
infects cells, reproduces itself, and spreads, the coronavirus relies on dozens of viral
and host proteins to complete its life cycle. The new oral pill paxlovid (Phizer)
inhibits the main viral protease used to create other proteins for the virus9 (REF. The
oral pill molnupiravir (Merck) inserts a defective RNA building block when the virus uses
an enzyme known as a polymerase to copy its genome. (REF Molnupiravir)8

The role of SARS-CoV-2new monoclonal antibodies in treatment of SARS-CoV-2 therapies
There are a number of factors that most probably will lead to seasonally peaks of
infection and hospital admissions for SARS-CoV-2 infections12-14. First, there will
remain a group within our population that remains willingly unvaccinated. Second, it is
shown that numerous immunocompromised patients have inadequate antibody response to
vaccinations and do not produce long-term protection15,16. At last, with new emerging
viral variants arising with expected higher viral spread, it is assumed that outbreaks of
SARS-CoV-2 infections will remain prevalent in the coming years12-14,17.

With regard to immunocompromised patients, even with the most effective mRNA SARS-CoV-2
vaccines show reduced or even absent humoral responses in patients with solid organ
transplants or for instance in patients treated with anti-CD20 for an hematologic
malignancy15,16. The fact that immunocompromised patients have inadequate immune response
to vaccinations underscores the need of treatment options essential for a subpopulation
to slow or stop the replications of the SARS-CoV-2 virus. Especially for these
immunocompromised patients the novel neutralizing monoclonal SARS-CoV-2 antibodies
therapies could become a real game changer.

First results of phase-III studies SARS-CoV-2 monoclonal antibodies

The first results of three several phase III placebo-controlled randomized controlled
clinical trials of monoclonal antibodies of SARS-CoV-2 are now available4,5,7,11. The
studies were designed to analyze the effect of these monoclonal antibodies when given
early after symptom onset to prevent disease progression, hospital admission and
mortality. Although these three studies are currently in pre-print, tTwo other studies
recently presented the preplanned interim analysis regarding the treatment of casirivimab
with imdevimab4 combination and the sotrovimab alone5. These two studies investigated a
single intravenously administration of monoclonal antibodies within 3-7 days after the
start of symptoms and demonstrated a relative reduction of 70-85% in Covid-19 related
hospital admission and death within four weeks4,18.

Due to the abovementioned evidence, the Dutch medical guideline for the treatment of
SARS-CoV-2 patients updated on July 20November, 2021. The Dutch Working Party on
Antibiotic Policy (Stichting Werkgroep AntibioticaBeleid, SWAB) now considers to treat
patients without a prior antibody response (that means no vaccination response and no
seroconversion) and with a high risk of Covid-19 disease progression to start treatment
with neutralizing monoclonal SARS-CoV-2 antibodies within 7 days after the start of
symptoms19. Patients with a high risk to develop severe Covid-19 are defined as follows
in the Dutch guidelines: age > 70 years, medical history of hematologic malignancy in the
last five years, severe kidney failure/dialysis, organ or bone marrow transplant, primary
immunodeficiency, Downs syndrome, neurologic disease in which the lung ventilation is
compromised, body mass index (BMI) >40, or using immunosuppressive medication or age > 60
years in combination with cardiovascular disease, chronic lung/ kidney disease or
diabetes 1920.

Before mid December, 2021,At the moment (early Jan 2022), casirivimab plus imdevimab are
were the only SARS-CoV-2 monoclonal antibody agents available in the Netherlands. Since
then,Of importance however, the B.1.1.529 (Omicron) variant of concern (VOC), which is
becoming the dominant variant in many parts ofacross the Netherlands, . This variant,
which has numerous mutations in the spike protein, is predicted to have markedly reduced
susceptibility to bamlanivimab plus etesevimab and casirivimab plus imdevimab. In line,
there is also considerable escape of SARS-CoV-2 Omicron to antibody neutralization by
bamlanivimab plus etesevimab. At this moment, sSotrovimab seems to beis the only
SARS-CoV-2 monoclonal antibody that is anticipated to have potent neutralisationactivity
against the Omicron mutantVOC. Therefore, the Dutch Working Party on Antibiotic adjusted
the advice regading the use of casivirmimab plus imdevimab on December 23, 2021.
Sotrovimab is expected to become available in the Netherlands in Q1 2022.

Oral SARS-CoV-2 antivirals Small-molecules for Covid-19 The mechanism of action of the
nucleoside analogue molnupiravir and the protease inhibitor nirmatrelvir/ritonavir
paxlovid areis independent of mutations in the spike protein, which can affect the
efficacy of monoclonal antibody treatments. The first results of twoa phase III
placebo-controlled randomized controlled clinical trials of molnupiravir oral antivirals
for Covid-19 are now available21. are now available. (REF molnupiravir, paxlovid).

Both oral antivirals are developed to be taken within the first few days of Covid-19
infection and are reported expected to reduce the risk of hospitalization and death by
approxiametly 30% for molnupiravir and even up tot 89% for nirmatrelvir/ritonavir
paxlovid and 30% for molnupiravir.9,21(REF molnupiravir and paxlovid). It should be noted
however that compete study results of nirmatrelvir/ritonavir are not yet available. In
addition, these compounds were tested in a non-vaccinated population.

The need for an independent Dutch cohort to evaluate the clinical use of neutralizing
monoclonalnew SARS-CoV-2 specific antibodiestherapies After the results of these first
results of phase-III studies4,5, these compoundsneutralizing monoclonal SARS-CoV-2
antibodies have been given an emergency use authorisation and - since late June 2021 -
have become available in the Netherlands to treat SARS-CoV-2 infected patients who are at
high risk to develop severe disease. Further randomized controlled trials investigating
the effect SARS-CoV-2 antibody in immunocompromised patients are expected to be deemed
unethical due to the clear effect seen in the phase-III trials and the already limited
existing immune response. Of interest, there are currently only intravenous antibodies
treatment regimens available, although the shift to different routes, most notably such
as subcutaneous and, intramuscular, oral and inhalation, is underway and will possibly
contribute to facilitated and larger access to these monoclonal antibodies. If adequate
safety profiles are shown with non-intravenous options a clinical admission could be
shortened or prevented. From a safety perspective, it is important to realize that escape
by SARS-CoV-2 viral variants have been described from neutralization by convalescent
plasma22. Because monoclonal antibodies require administration by means of infusion or
injection in a medical setting, oral agents such as molnupiravir and
nirmatrelvir/ritonavir paxlovid that can be administered by the patient at home shortly
after diagnosis, may be more practical and patient-friendly for nonhospitalized
personspatients9,21. As a result, these; such agents are considered would be important
new tools in the Covid-19 treatment armamentarium. Another advantage of these oral
antivirals over SARS-CoV-2 spike protein-directed monoclonal antibodies is their
potential efficacy of against emerging SARS-CoV-2 variants. After the initial results, of
the phase III studies (REF paxlovid & molnupiravir), the oral antivirals have been given
a FDAn emergency use authorization since late December 2021 by the FDA8,9. Molnupiravir
and paxlovid is expected to will become available in the Netherlands in Q1 2022
(nirmatrelvir/ritonavir perhaps in Q2/Q3)February and during the spring, respectively, in
the Netherlands. will be available in February and paxlovid in the spring in the
Netherlands..

ThisThe above underscores the need to establish a cohort and biobank of patients treated
with these compounds in order to monitor this long term outcomes in a real world setting.

Now, urgent key questions need to be addressed to allow the most efficacious use of these
novel and potentially lifesaving treatments. Which patient categories will benefit most
from these new drugs? What is the safety profile in immunocompromised patients? This
study aims to establish a prospective cohort of all patients treated with neutralizing
monoclonalnew specific SARS-CoV-2 antibodies therapies to evaluate its real world effect,
effect on the host response and safety.

3. OBJECTIVES

Primary Objectives:

To assess effect on the host response and safety of novel SARS-CoV-22 2 monoclonal
antibody treatment:therapies.

- A. What are the SARS-CoV-2 viral load kinetics during and after treatment with
neutralizing monoclonalnew SARS-CoV-2 antibodiestherapies?

- B. Do SARS-CoV-2 variants, spike mutations and immune escape during treatment with
neutralizing monoclonal new SARS-CoV-2 antibodiestherapies?

- C. What are the SARS-CoV-2 antibody and inflammatory response kinetics during and
after treatment with neutralizing monoclonalnew SARS-CoV-2 antibodiestherapies?

- D. To create a biobank to address future questions regarding the current use of
neutralizing monoclonalnew SARS-CoV-2 antibodies therapies compared to novel
COVID-19 treatments which are in development.

4. STUDY DESIGN

The TURN-COVID biobank will be a prospective cohort study designed in accordance with
international standards23. The study population will consist out of all patients treated
with monoclonal SARS-CoV-2 antibodies and small-molecules for Covid-19.; this will be
primarily patients admitted on the day care facilities for single intravenous dose of
neutralizing monoclonal SARS-CoV-2 antibodies but could also include patients that are
admitted to the hospital for Covid-19 (see study population). Clinical data will be
obtained throughout the electronic patient dossier.

Oropharyngeal swabs and blood samples as detailed below will be sampled at day 0, 7, 28
and 90. A two day deviation before and after the appointment is deemed acceptable for day
0 and day 7. For day 28 and day 90 a seven day deviation is deemed acceptable.. Samples
will be stored in the Amsterdam UMC, location AMC. The design is further visualized
schematically in Figure 1.