An exploratory study to evaluate in vivo, ex vivo and clinical hypersensitivity reactions after first-time treatment with complement-reactogenic infusions

Complement activation related pseudoallergy (CARPA) is a type of
infusion-related reaction (IRR) in which unintentional overactivation of the
complement system leads to symptoms of hypersensitivity. CARPA is thought to be
primarily caused by the production of anaphylatoxins C3a and C5a, which lead to
non-IgE-mediated skin reactions, heart rate and blood pressure alterations and
risk of cardiogenic shock.

In vitro studies by Szebeni et al have shown that CARPA reactions may be evoked
by a variety of compounds. However, structurally complex formulations such as
liposomes and polyethyleneglycol(PEG)ylated-protein structures have been
particularly associated with the induction of CARPA in vitro. Paclitaxel, a
surfactant-based taxane has been shown to induce CARPA in vitro, which may be
an effect of its surfactant excipient rather than the active ingredient.
Therefore, albumin-bound paclitaxel (Abraxane) has been developed, with the
purpose of relieving these hypersensitivity reactions. A similar response has
been described for Amibsome, the liposomal formulation of Amphotericin B.
Furthermore, the pegylated liposomal formulation of doxorubicine (Caelyx), has
been described to activate complement both in vitro and in vivo. Chanan-Khan et
al have shown that first- time exposure to liposomal doxorubicin (Caelyx) leads
to elevated levels of complement sC5b-9 in vivo, which was associated with the
occurrence of IRRs. The presence of elevated levels of anaphylatoxins C3a and
C5a which are thought to be the drivers of CARPA symptoms remains unknown. The
contribution of other complement proteins to the development of clinical
symptoms also needs to be elucidated.

The first steps in unravelling the role of complement in infusion-related
reactions (IRRs) have been taken. However, IRRs in general, and more
specifically human in vivo CARPA reactions remain underreported and
understudied, whilst the impact of CARPA on clinical trial participants,
clinical site staff and the general drug development process is significant.
Moreover, infusion reactions severely disrupt routine care, burdening both the
patient and the clinical team. Therefore, efforts to recognize and further
understand CARPA induction have been made at the Centre for Human Drug
Research. We performed in vitro challenge experiments, where serum or plasma is
incubated with potentially CARPA reactogenic compounds in line with the
approach suggested by Szebeni et al. These ex vivo experiments can be used to
evaluate potential complement activation by investigational compounds.
Furthermore, the assays can help us gain a deeper understanding of in vivo
CARPA reactions by mapping out the role of individual complement proteins in
the development of clinical signs and symptoms. Finally, these challenge
experiments may be further developed and standardized with the purpose of
assessing individual CARPA sensitivity, with the ultimate goal of establishing
the risk of CARPA induction in an individual prior to in vivo dosing. If- and
how the ex vivo challenge experiments translate to in vivo induction of CARPA
remains to be elucidated.

Primary Objectives
• To evaluate in vivo complement activation after first-time treatment with
paclitaxel, liposomal doxorubicin (Caelyx) or other complement-reactogenic
compounds
• To evaluate ex vivo complement activation after incubation of predose samples
with paclitaxel or liposomal doxorubicin

Secondary Objectives
• To evaluate the occurrence of clinical CARPA symptoms in relation to in vivo
complement levels

This is a multi-center, exploratory, observational study to evaluate in vivo
and ex vivo complement activation after first-time treatment with therapeutic
agents, including liposomal doxorubicin and paclitaxel. Up to 60 patients
receiving first-time treatment with paclitaxel or liposomal doxorubicin will be
included. 60 patients would be a relevant sample size for an exploratory study,
as based on the described incidence of clinical CARPA of 5-10% in the
pre-medicated population, a minimum of 3 clinical events is expected to occur.
The incidence of subclinical events is expected to be at least similar but
likely higher, as the limited amount of literature available describes elevated
levels of complement in absence of clinical symptoms.

An interim analysis will be conducted after every 15 patients, which will
consist of a review of the following relevant events:
1. Observation of clinical CARPA signals after first-time treatment with
complement-reactogenic agents including: Flushing, Itching, Alterations in
heart rate and blood pressure, Respiratory symptoms, Back- or abdominal pain,
Gastrointestinal symptoms, Skin reactions, Angioedema, Temperature changes,
Dysgeusia (metallic taste).
2. Observation of subclinical signs of complement activation after first-time
treatment with complement-reactogenic agents: post-dose elevated levels of
complement-activation products including C3a, C3d and/or sC5b9 in vivo,
evaluated against baseline.

If >=1 event occurs, the study will be continued, and another 15 patients will
be enrolled. In case of absence of a relevant signal and/or emerging CARPA
signals with other therapeutic compounds within the study population,
additional subjects may be included. All patients will be treated according to
local treatment protocols, including any applicable pre-medication. No
modifications will be made to the treatment strategy. Patients will be
evaluated for symptoms of IRRs in an observational manner. Serum and plasma
samples will be collected pre-infusion and at 10 min, 30 min and 1 hour
post-start-infusion. Additional samples may be collected upon signs of IRRs
outside of the defined timepoints. Additional samples may also be collected in
case the duration of the first treatment is extended (e.g. due to cold cap
treatment). The total duration of the study period will correspond with the
duration of the treatment per local protocols

The overall aim of this study is to study complement activation and
CARPA-symptoms in patients that are being treated with complement-reactogenic
compounds to gain a deeper understanding of the mechanisms involved in human,
in vivo CARPA induction. Additionally, we aim to investigate the relationship
between ex vivo complement activation in the assay and in vivo occurrence of
CARPA symptoms in an exploratory manner. No medical benefit can be expected
form this study for the participating subjects.

No modifications will be made to the treatment protocols or strategies of
included patients. Patients will be evaluated for signs of IRRs during the
treatment period in an observational manner and will receive an additional
intravenous cannula to collect blood for the purpose of this study.
Approximately 110mL of blood will be collected which may result in minor
discomfort or a bruise but is not expected to have further negative impact on
the patient. Any patients who have poor venous access limiting phlebotomy or
any other condition that would, in the opinion of the investigator, potentially
compromise the safety of the patient will be excluded