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Problem

The current solution is the usage of statins. But there are many potential downsides. Some of these downsides include liver damage and muscle related side effects. Conventional medications, including the class statins or the medication Ezetimibe, can have several side effects that reduce patient adherence and quality of life. Other types of medications can have prohibitive costs, preventing patients from accessing medications more suited to them.

86 million U.S. adults aged 20 or older
have total cholesterol levels above the
normal of 200 mg/dL.¹

Globally, 4.4 million deaths
were attributed to high LDL cholesterol
levels in 2019.²

Purpose

When considering the limitations and side effects associated with current high cholesterol medications, we recognised the need for an alternative. Therefore, we developed CholesterLock, a proof of concept for an alternative cholesterol-lowering medication.

CholesterLock is a proof-of-concept for a novel protein therapeutic aimed at reducing high cholesterol levels, and preventing downstream health issues worsened or caused by high cholesterol. This protein therapeutic would be an orally administered medication for the digestive tract, released into the intestines primarily in order to inhibit the NPC1L1 receptor. Our goal is to make CholesterLock a safer and more affordable option for dealing with high cholesterol.

Target

Our alternative centers around an engineered fusion protein capable of travelling to the small intestine and targeting the receptor NPC1L1.

The Niemann-Pick C1-Like 1 (NPC1L1) is a transmembrane protein found primarily in the liver and intestines in humans.³ Its primary function is mediating cholesterol absorption, which is why it is the target of the commonly prescribed drug Ezetimibe. This drug is a cholesterol absorption inhibitor used to treat high cholesterol, and the inhibition of NPC1L1 has been shown to lower cholesterol absorption, and is believed to be involved in fatty acid absorption.⁴

The aim of CholesterLock is to mimic the action of Ezetimibe and inhibit the NPC1L1 receptor, with fewer off-target side effects. By inhibiting the NPC1L1 receptor, CholesterLock could lower both the amount of cholesterol absorbed through the diet, and synthesised cholesterol which varies between people.

Mechanism

Cholesterol is first captured and recruited to NPC1L1 by binding its N-terminal domain.³ Upon interaction, NPC1L1 switches from an open state to a closed state, creating a tunnel between the initial recruitment site to a region called the sterol sensing domain within the plasma membrane. The cholesterol is transported from its point of capture to the outer leaflet of the membrane where it will begin to accumulate. This accumulation signals both NPC1L1 and the cholesterol to come into the cell.

If we can prevent cholesterol from ever even binding NPC1L1 at the N-terminal, we can inhibit the entire mechanism of cholesterol intake in intestinal cells right from the start.

Solution

Our engineered fusion protein consists of three key components and combines features from two proteins: Immunoglobulin Gamma (IgG) and Sonic Hedgehog protein. IgG serves as a transporter protein, known for its stability even in gastrointestinal conditions.⁵ We included its Fc fragment to provide stability and act as a chaperone. Next, we included a fragment of Sonic Hedgehog protein, which plays a vital role. In the presence of cholesterol, hedgehog protein undergoes a process called autoproteolysis, where the protein is cleaved into two fragments: the C-terminal and the N-terminal.⁶ During this process, a cholesterol molecule is attached to the end of the N-terminal domain. We can use this cholesterol modification to allow our fusion protein to bind the initial recruitment site on NPC1L1, blocking additional cholesterol molecules from interacting with the receptor.