Welcome to Centessa Pharmaceuticals' presentation of preclinical data for ORX750, our first development candidate for the treatment of narcolepsy and other sleep-wake disorders, which was also presented in an oral session at the World Sleep Congress. A copy of the company's press release issued today detailing these data, as well as the slides from today's presentation, are available on our investor relations website. Joining me for today's event are Dr. Mario Alberto Accardi, President of Centessa's Orexin Agonist Program, and Dr. Sarah Wurts Black, Head of Biology for Centessa's Orexin Agonist Program. Doctors Accardi and Black are joining us from Rio de Janeiro, where Dr. Black delivered the oral presentation for ORX750 at World Sleep earlier today. Before turning the call over to Dr. Accardi, I'd like to remind everyone that this presentation includes forward-looking statements.
Each forward-looking statement contained in this presentation is subject to risks and uncertainties that could cause actual results to differ materially from those described, projected, or implied in these statements. Additional information regarding these risk factors are described in the forward-looking statements section of the slides for today's presentation, as well as in the Risk Factors and Management's Discussion and Analysis section of our most recent quarterly and annual reports filed with the SEC, and can also be found on our website at centessa.com. The forward-looking statements within this presentation speak only as of the original date of this event, and we do not undertake any obligation to update or revise these statements. With that, I'd now like to turn the presentation over to Dr. Accardi, President of Centessa's Orexin Agonist Program. Dr. Accardi?
Thank you, Kristen, and welcome everyone. It's great to be here with you to discuss a robust set of new preclinical data for our investigational novel orexin-2 agonist, ORX750, that was presented here today at the World Sleep Congress. We're excited to share this data, which we believe support ORX750's potential best-in-class profile for the treatment of narcolepsy and other sleep-wake disorders. Of course, subject to review and approval. Before I hand the event over to Dr. Black to detail the data, it would be helpful to take a step back and provide some background on our orexin program. I'll also give some high-level thoughts about the data presented today. This is an exciting time for narcolepsy patients, as orexin agonists are well-validated targets and have long been sought as a potential therapeutic to address the underlying cause of narcolepsy type 1, or NT1.
Narcolepsy is a chronic neurological disorder that disrupts the brain's ability to regulate the normal sleep-wake cycle. It is estimated to affect over 150,000 people in the U.S. and over 3 million people worldwide. Approximately 50% of narcolepsy patients have NT1, a condition distinguished by the presence of cataplexy and loss of orexin tone. The link between the loss of orexin and NT1 was first discovered by Dr. Emmanuel Mignot, who today serves as the chair of Centessa's Orexin Scientific Advisory Board. Narcolepsy type 2, or NT2, is characterized by excessive daytime sleepiness, or EDS, with no cataplexy, and unlike NT1, individuals with NT2 typically have normal orexin levels. Presently, only palliative treatments are available for NT1 and NT2.
Approved treatments often include polypharmacy approaches, which focus on addressing the symptoms of the disease but do not address the underlying cause. It has been reported that of those patients currently being treated, approximately 75% still suffer from EDS, and approximately 50% continue to experience one to two episodes of cataplexy per day. There is a significant unmet need for new treatment options. We believe orexin agonists have the potential to address the root cause of NT1 by directly compensating for the loss of orexinergic neurons and providing what could function as an orexin replacement therapy. We believe this targeted approach has the potential not only to transform the treatment of NT1, but also to address EDS and other rare hypersomnias, such as NT2 and idiopathic hypersomnia. We believe this represents a substantial multibillion-dollar market opportunity.
Only half of narcolepsy patients are believed to be diagnosed, and of these diagnosed patients, only 25% are estimated to be on treatment. Therefore, we believe more effective therapies could significantly expand this potential market opportunity. In addition, we see potential application of orexin agonists to combat excessive daytime sleepiness in more prevalent disorders, including Parkinson's disease, atypical depression, and other diseases. Targeting the orexin-2 receptor with an agonist is a highly complex medicinal chemistry challenge. Designing a brain penetrant, highly potent, and selective molecule that can mimic the precise binding and activating properties of the native ligand, which is approximately sevenfold larger in size than the other small molecule drugs, is an extremely difficult task. Centessa's Orexin Agonist Program seeks to address these challenges with structure-based drug design.
Through a collaboration with Sosei Heptares, a world leader in GPCR drug design, we obtained exclusive access to unique structural biology capabilities, which have helped guide our medicinal chemistry team to design highly potent molecules and assemble multiple series of orexin agonists, which are wholly owned by Centessa. As you can see on this slide, Centessa's Orexin team includes recognized leaders, including Doctors Deborah Hartman, Sarah Wurts Black, Amy Lange-DOrati , and Professor Emmanuel Mignot. These team members have deep expertise in orexin discovery and development, having previously led preclinical and clinical orexin agonist programs. The combination of our technology and team has enabled us to discover and nominate our first development candidate in this field, ORX750, an orally administered, selective orexin-2 receptor agonist.
We're also exploring additional follow-up orexin agonists, which we believe have the potential to be progressed towards different indications and therefore potentially unlock further market opportunities. Now on to ORX750. The headline for the preclinical data presented today at Sleep is that ORX750 is a full orexin receptor 2 agonist that potently agonizes the orexin-2 receptor with an in vitro EC50 of 0.11 nM or 110 pM. This is a remarkable finding because this in vitro result suggests ORX750 is almost as potent as the native orexin A peptide. In a highly predictive translational NT1 mouse model called the DTA model, the data showed oral administration of ORX750 achieved maximal wake time and suppressed cataplexy at the lowest dose tested, which was 0.1 mg/kg.
The data showed ORX750 also significantly increased wake time in wild-type mice with normal orexin tone, which we believe suggests the potential for indication expansion beyond NT1. In summary, we believe ORX750 has a potential best-in-class profile for the treatment of narcolepsy and other sleep-wake disorders. Again, subject to review and approval. To tell you more about ORX750, it is now my pleasure to turn the call over to Dr. Sarah Wurts Black, Head of Biology for Centessa's Orexin Agonist Program. By way of introduction, Dr. Black has an extensive 30-year career in basic and applied neuroscience of sleep. She was a postdoctoral fellow at Stanford University and professor in Emmanuel Mignot's lab. Dr. Black also contributed to the creation of the DTA mouse model of orexinergic neuron loss.
Prior to coming to Centessa, Dr. Black was the leader of in vivo biology at Reset Therapeutics. Dr. Black?
Thank you, Dr. Accardi. ORX750 is a novel orexin receptor 2 agonist that has been designed to treat the underlying cause of narcolepsy type 1 or NT1. NT1 is a neurological disorder in which the neurons that produce orexin are lost, resulting in a dramatic reduction of orexin levels in the brain. ORX750 has been designed to replace that lost orexin as a potential new treatment for NT1 and also for other sleep-wake disorders in which orexin neurons are present. This presentation will introduce the preclinical profile of ORX750 for its selection as a clinical candidate for NT1. In our in vitro preclinical studies, ORX750 was highly potent and selective for the OX2 receptor, and it was developed using structure-based drug design with high-resolution protein crystallography and cryo-EM.
The in vitro EC50 was 0.11 nM at the human OX2R receptor. We believe this high potency, combined with biophysical properties that predict high CNS penetration, supports the potential for ORX750 to be efficacious at very low doses. As follows, ORX750 showed strong preclinical activity in alleviating NT1 symptoms in highly predictive mouse models in which the orexin neurons are absent. In humans, two of the main symptoms of NT1 are excessive daytime sleepiness and cataplexy, which is the sudden loss of muscle tone, often triggered by strong emotions. In NT1 model mice, ORX750 promoted wakefulness and suppressed cataplexy at the lowest dose tested, which was 0.1 mg/kg .
ORX750 also promoted wakefulness in wild-type mice, in which the orexin neurotransmitter system is intact and functional, which may support indication expansion beyond NT1. In the in vitro FLIPR assay, in which activation of the OX2 or OX1 receptors was measured by calcium mobilization, ORX750 showed it was a full agonist and showed very high subnanomolar potency, with an EC50 of 0.11 nM at the OX2 receptor. The dose response is shown by the orange curve. To achieve this potency with a small molecule is remarkable because it's very close to that of the native peptide ligand, orexin A or OXA, shown by the gray curve. ORX750 was also highly selective for the OX2 receptor. The blue curve shows activation at an OX1 receptor at much lower potency.
In other in vitro assays, ORX750 was shown to activate the same intracellular pathways as OXA, have similar potency at recombinant OX2 receptors in human, mouse, rat, dog and monkey systems, and it displayed clean profiles in selectivity and safety panels. We interpret these results to mean that ORX750, as a therapeutic replacement for lost OXA, should activate OX2 receptors in a similar way as the native ligand. It's important to show that ORX750 works in a brain region that, when activated, is known to promote wakefulness. We sought to show that using the ex vivo brain slice assay, which was designed to show that ORX750 activated endogenous OX2 receptors. In this assay, electrophysiological recordings are made from live neurons that are part of the wake-promoting neurocircuitry.
That is histaminergic neurons in the ventral tuberomammillary nucleus or TMN, where the OX2 receptor is abundant, and the OX1 receptor is relatively absent. This trace from a representative cell shows how the firing rate of the neuron increased during application of ORX750. In vivo efficacy of ORX750 was tested in two established translational NT1 mouse models, in which the orexin-producing neurons are lost and the same symptoms occur as in the human condition. Both of these models, the Atax and the DTA mouse, have been shown to be predictive of pharmacological activity in humans. The DTA mouse tends to show more severe symptoms than the Atax mouse, so we use both models to capture a wide range of symptom severity. In these models, we measured arousal states using EEG and EMG with concurrent video in a counterbalance study design.
That means all mice received all treatments, and all treatments were represented on each recording day, with 72 hours of washout between doses. ORX750 promoted wakefulness, as shown by two measures. First, the amount of time that the mice were awake in the three hours post-dose, shown in the top in blue. ORX750 achieved maximal efficacy in this assay. The mice were awake for 91% of the time after the lowest doses tested, down to 0.1 mg/ kg in the DTA mouse model. Secondly, the length of time it took for the mice to return to sleep after dosing, that is the sleep latency, shown in the bottom in orange, showed a dose response in both models, starting at the lowest doses tested.
The maximum effect observed was fivefold over vehicle in the Atax mice and ninefold over vehicle in the DTA mice. Note that the dose ranges differed between models. We performed the Atax study first, and after observing activity at 0.3 mg/kg, we stepped down the doses for the next study in the DTA mice. So even in a model of NT1 with severe symptoms, ORX750 was able to increase wakefulness. In the same mice, and from the same study as the previous slide, ORX750 also suppressed cataplexy with an apparent dose response, and at the lowest dose tested in the DTA mouse, 0.1 mg/kg. The number of cataplexy occurrences decreased with dose, shown in the top in blue. The maximum responses were tenfold and sixfold in the Atax and DTA mice, respectively.
The latency to the first appearance of cataplexy increased, shown in the bottom panels in orange. The maximum effect was three- to four-fold for both models. In a follow-on study, the suppression of cataplexy and the promotion of wakefulness was maintained after 14 days of treatment. The wakefulness induced by ORX750 in Atax mice featured changes in the EEG power spectra that are consistent with enhanced alertness. Gamma power increased and theta power decreased in a dose-related manner in the first hour post-dose in Atax mice, and alpha power was also increased. ORX750 also showed activity in healthy wild-type mice, in which the orexin system is intact and functional. These data were collected in the PiezoSleep assay, in which physiologically relevant readouts based on body movement and breath rate have been validated to highly correlate with EEG-defined sleep-wake measures.
Here, we showed that ORX750 increased wake time, shown in the orange panels, and increased the consolidation of wakefulness, shown in the blue panels, in wild-type and Atax colony mates. In wild-type mice, time awake increased in a dose-related manner and was evident at the lowest dose tested, 1 mg/kg . In Atax mice, time awake achieved maximal effect during the two hours post-dose, down to the lowest dose tested, 0.3 mg/kg . This increased sensitivity to orexin agonism in NT1 model mice was expected, and it's why a lower dose range was used for them versus the wild-type mice. Wakefulness was also consolidated after ORX750 in both Atax and wild-type mice. That is, as the dose increased, wake bouts were longer, and therefore there were fewer of them.
These results in wild-type animals are important because we believe that they support the potential for indication expansion into disorders with normal orexin levels. To summarize, ORX750 is a novel full orexin-2 receptor agonist, and it's characterized by a combination of high potency, close to that of OXA, coupled with high selectivity that together confer robust preclinical activity shown in NT1 model mice, as well as in healthy orexin-intact wild-type mice. All of these results support further progression of ORX750 as a potential new treatment for narcolepsy as well as other hypersomnia disorders. Thank you. I'll now turn the presentation back over to Dr. Accardi.
Thank you, Dr. Black. To wrap up today's presentation, we believe these data are very encouraging and further support a potential best-in-class profile for ORX750 for the treatment of narcolepsy and other sleep-wake disorders, subject, of course, to review and approval. We are focused on rapidly moving ORX750 through IND-enabling studies, obtaining IND clearance, and initiating clinical development of ORX750, with the goal of sharing clinical proof -of -concept data in 2024. If you have any questions, please reach out to Investor Relations. Thank you.