Business description of Solid-Biosciences-Inc from last 10-k form

Overview

Our mission is to cure Duchenne muscular dystrophy, or DMD, a genetic muscle-wasting disease predominantly affecting boys, with symptoms that usually manifest between three and five years of age. DMD is a progressive, irreversible and ultimately fatal disease that affects approximately one in every 3,500 to 5,000 live male births and has an estimated prevalence of 10,000 to 15,000 cases in the United States alone. DMD is caused by mutations in the dystrophin gene, which result in the absence or near-absence of dystrophin protein. Dystrophin protein works to strengthen muscle fibers and protect them from daily wear and tear. Without functioning dystrophin and certain associated proteins, muscles suffer excessive damage from normal daily activities and are unable to regenerate, leading to the build-up of fibrotic, or scar, and fat tissue. There is no cure for DMD and, for the vast majority of patients, there are no satisfactory symptomatic or disease-modifying treatments. Our lead product candidate, SGT-001, is a gene transfer under investigation for its ability to drive functional dystrophin protein expression in patients’ muscles. Based on our preclinical program that included multiple animal species of different phenotypes and genetic variations, we believe the mechanism of action of SGT-001, if our clinical trials prove to be successful, has the potential to slow or even halt the progression of DMD, regardless of the type of genetic mutation or stage of the disease.

SGT-001 has been granted Rare Pediatric Disease Designation, or RPDD, and Fast Track Designation, in the United States and Orphan Drug Designations in both the United States and European Union. The safety and efficacy of SGT-001 are currently being evaluated in a Phase I/II clinical trial called IGNITE DMD.

For patients suffering from DMD, symptoms usually begin to manifest between three and five years of age, when they fail to reach developmental milestones or experience motor function challenges, such as difficulty walking or climbing stairs. As the disease progresses, patients with DMD experience frequent falls; can no longer run, play sports or perform most daily functions; and are further weakened by physical activity. By their early teens, DMD patients typically lose their ability to walk and ultimately become dependent on a wheelchair for mobility. By their 20s, patients essentially become paralyzed from the neck down and require a ventilator to breathe. Though disease severity and life expectancy vary, a DMD patient’s quality of life dramatically decreases over time, with death typically occurring by early adulthood from either cardiac or respiratory complications.

Our founders, who are personally touched by the disease, created a biotechnology company purpose-built to accelerate the discovery and development of meaningful therapies for all patients affected by DMD. Through this disease-focused business model, our research team, led by experts in DMD biology and drug development, along with key opinion leaders in DMD, continuously evaluate emerging science to identify high-potential product candidates. Our selection process includes extensive diligence and initial pharmacology research with highly specific, predefined criteria, which provide us with confidence in our development program decisions. Through this data-driven selection process, we have evaluated a number of programs and identified gene therapy as a potentially beneficial approach for DMD, and thus initiated development of our lead product candidate SGT-001. We will continue to apply this rigorous approach and reject the majority of the candidates we evaluate in our effort to develop only programs that we believe have the greatest likelihood of becoming therapies for DMD patients.

Our product candidates

SGT-001 is our lead gene transfer candidate. Gene transfer, a type of gene therapy, is designed to address diseases caused by mutated genes through the delivery of functional versions of those genes, called transgenes. The transgenes are then utilized by the body to produce proteins that are absent or not functional prior to treatment, potentially offering long-lasting beneficial clinical effects. SGT-001 is designed to address the underlying genetic cause of DMD by delivering a synthetic transgene that produces dystrophin-like protein that is only expressed in muscles of the body, including cardiac and respiratory muscles. Our SGT-001 vector is derived from a naturally occurring, non-pathogenic virus called adeno-associated virus, or AAV, which was selected for its ability to efficiently enter skeletal, diaphragm and cardiac muscle tissues. The vector is designed to carry a synthetic dystrophin transgene construct, called microdystrophin, that retains the most critical components of the full-size dystrophin gene yet is small enough to fit within AAV packaging constraints. SGT-001 is designed to drive microdystrophin protein expression in affected muscles throughout the body. In our Investigational New Drug Application-, or IND, enabling preclinical program, we have studied the efficacy, safety and durability of SGT-001 in multiple preclinical models and its functional benefits in DMD animal studies. In contrast to other therapeutic approaches that are designed to target specific mutations in the dystrophin gene, we believe SGT-001 is a mutation agnostic approach.

In the fourth quarter of 2017, we initiated a randomized, controlled, open-label, single-ascending dose Phase I/II clinical trial, called IGNITE DMD, to evaluate SGT-001 in ambulatory and non-ambulatory males with DMD aged four to 17 years. The primary objectives of IGNITE DMD are to assess the safety and tolerability of SGT-001, as well as efficacy as defined by microdystrophin protein expression. The clinical trial is also designed to assess muscle function and mass, respiratory and cardiovascular function, serum and muscle biomarkers associated with microdystrophin production, patient reported outcomes and quality of life measures, among other endpoints. IGNITE DMD is anticipated to enroll 16 to 32 patients with DMD.

In February 2019, we announced preliminary findings based on three-month biopsy data from the first three patients dosed with 5E13 vg/kg of SGT-001, the lowest dose outlined in the study protocol. In one patient, microdystrophin was detected via western blot below the five percent level of quantification of the assay and in approximately 10 percent of fibers via immunofluorescence. There were also signs of co-localization of neuronal nitric oxide synthase (nNOS) and beta-sarcoglycan associated with microdystrophin expression. In the second and third patients, microdystrophin was detected via immunofluorescence at very low levels, but it was undetectable via western blot. Based on our preclinical data, we believe that a higher dose of SGT-001 may result in meaningfully higher levels of microdystrophin protein. Therefore, we have amended the protocol to dose escalate after three patients have been dosed instead of after four patients as originally planned.  In addition, we received approval from the IGNITE DMD clinical study Data Safety Monitoring Board, or DSMB, and University of Florida Investigational Review Board, or IRB, to begin dosing the next cohort of patients at 2E14 vg/kg. We plan to continue enrolling children in this cohort as soon as possible and intend to resume dosing adolescents in the future.

Based on additional data from the clinical trial we will determine next steps for SGT-001 clinical development, including additional clinical trials that may include other patient populations, as well as the need for larger confirmatory clinical trials.

If successfully developed and approved, we intend to commercialize SGT-001, and we may enter into licensing agreements or strategic collaborations to do so in select markets.

Taking into account the prevalence and incidence of DMD and the anticipated dosing requirements for gene transfer, we anticipate that there will be a need for a substantial supply of SGT-001 for clinical trials and, if approved, for commercial markets. Through significant targeted investments to address this challenge, we have developed a manufacturing process that we believe can scale to adequately meet our needs for clinical trials, commercial launch and beyond.

While we believe gene transfer may be able to slow or halt DMD disease progression, many patients would still suffer from the manifestations of the disease, such as tissue damage to their muscles, inflammation, cardiac dysfunction and fibrosis. As part of our disease-focused business model, we are also building a portfolio of complementary disease modifying therapies to address these manifestations. Our portfolio currently includes an initial disease modifying candidate, Anti-LTBP4, a monoclonal antibody designed to reduce fibrosis and inflammation, as well as a number of emerging and complementary programs. Preclinical activities for the Anti-LTBP4 program are on-going.

In addition to developing our pipeline of product candidates, we believe it is critical to invest time and resources in tools and technologies designed to help us more effectively understand DMD, accurately monitor disease progression and assist patients in daily life. As part of this goal, we are developing biomarkers and sensors that may allow us to identify treatment targets faster, measure the therapeutic impact of potential product candidates better and reach decision points earlier. In addition, through our Solid Suit program, we are developing wearable assistive devices with the goal of providing functional and therapeutic benefits to DMD patients.

Our pipeline

We seek to protect our proprietary and intellectual property position through a combination of patents, trade secret laws, proprietary know-how, continuing technological innovation, and entering into non-disclosure, confidentiality and invention assignment agreements. For our gene transfer programs, we have exclusively licensed three issued U.S. patents, one pending U.S. non-provisional patent application, and seven issued patents and eleven pending patent applications in foreign jurisdictions. We have filed four pending U.S. provisional patent applications, two pending PCT international patent applications, and two pending patent applications in Taiwan. We intend to continue building out our intellectual property protection to further strengthen our position in the DMD field.

Who we are

Solid Biosciences was founded in 2013 by our Chief Executive Officer, Ilan Ganot, our Chairman of the Board, Andrey Zarur, our former President, Gilad Hayeem, our board member Matthew Arnold and our Head of Patient Advocacy Annie Ganot, with the goal of developing meaningful therapies for patients with DMD. Solid is the English translation of Eytani, the Hebrew name of Ilan and Annie Ganot’s son, who was diagnosed with the disease in 2012. Our founders, unsatisfied with the existing therapeutic landscape, proceeded to raise funds to execute on our disease-focused business model. We assembled a passionate management team and scientific advisory board composed of individuals with extensive experience in DMD, gene therapy, product discovery, research and development, manufacturing, business strategy and finance.

In 2015, we began exclusively licensing the elements of the construct for SGT-001 and other elements of our gene transfer program from the University of Michigan, the University of Missouri and the University of Washington. Since then, we have continued to use our extensive network across the academic, business and patient communities to identify, vet and pursue high-potential complementary product candidates to address the needs of DMD patients.

Since our inception, we have raised private capital from a group of top-tier corporate and private investors. In addition, three leading U.K.-based DMD charities provided initial seed funding for our gene transfer program in return for equity in our company, and we have accepted additional contributions from several DMD charities to fund our early-stage research programs. In January 2018, we completed our initial public offering resulting in net proceeds of $129.1 million, after deducting underwriting discounts and commissions and offering expenses.

We operated as a Delaware limited liability company under the name Solid Biosciences, LLC until immediately prior to the effectiveness of our registration statement on Form S-1 on January 25, 2018, at which time we converted into a Delaware corporation pursuant to a statutory conversion and changed our name to Solid Biosciences Inc.

Mission

Our mission, which guides every aspect of our operations, is to cure DMD. Underscoring this mission, our disease-focused business model is founded on the following fundamental values:

About Duchenne muscular dystrophy

DMD is an X-chromosome-linked, muscle-wasting disease, predominantly affecting boys. Progressive, irreversible and ultimately fatal, DMD occurs in approximately one in every 3,500 to 5,000 live male births and has an estimated prevalence of 10,000 to 15,000 cases in the United States alone. In DMD, mutations in the dystrophin gene result in the body’s inability to produce functioning dystrophin protein, which works to strengthen muscle fibers and protect them from daily wear and tear. Dystrophin protein also serves as the cornerstone of the dystrophin glycoprotein complex, or DGC, a group of proteins that links the inner and outer components of muscle cells to ensure proper muscle function.

Without dystrophin and the DGC, muscles suffer excessive damage from normal daily activities and are unable to regenerate, leading to the build-up of scar and fat tissue. More than 1,000 dystrophin gene mutations, which can be inherited or can occur spontaneously, have been identified in people with DMD.

For patients suffering from DMD, symptoms usually begin to manifest between three and five years of age, when they fail to reach developmental milestones or experience motor function challenges, such as difficulty walking or climbing stairs. Muscle wasting initially presents in the legs and pelvic area, then in the muscles of the shoulders, neck and arms. As the disease progresses, patients with DMD experience frequent falls, can no longer run, play sports or perform most daily functions, and are further weakened by physical activity. In addition to physical challenges, DMD also commonly involves cognitive difficulties and behavioral challenges.

By their early teens, DMD patients typically lose their ability to walk and become dependent on a wheelchair for mobility. By their 20s, patients essentially become paralyzed from the neck down and require a ventilator to breathe. Though disease severity and life expectancy vary, a patient’s quality of life dramatically decreases over time, with death typically occurring by early adulthood from either cardiac or respiratory complications.

Need for effective therapies

Glucocorticoid treatment, the current standard-of-care, has been shown to temporarily improve muscle strength, prolong the period of ambulation and slow the progression of DMD. However, glucocorticoid use is associated with well-known adverse events, such as severe weight gain, stunted growth, weakening of bone structure and metabolic dysfunctions, among others. The most commonly used glucocorticoids include prednisone and deflazacort (EMFLAZA).

In recent years, certain regulators have conditionally approved two new therapies, eteplirsen (EXONDYS 51) and ataluren (Translarna), which target specific mutations in the dystrophin gene. These therapies are indicated for only a small portion of the DMD patient population, and their respective efficacy profiles still need to be fully understood.

Eteplirsen is an antisense oligonucleotide indicated for DMD patients who have a confirmed mutation of the dystrophin gene amenable to exon 51 skipping, which affects approximately 13% of DMD patients. Eteplirsen is administered as a weekly intravenous infusion. In 2016, eteplirsen was granted accelerated approval from the U.S. Food and Drug Administration, or FDA, based on an increase in dystrophin in skeletal muscle observed in some patients who received the therapy. However, the FDA concluded that a clinical benefit, including improved motor function, has not been established. As of September 21, 2018, the European Medicines Agency’s or the EMA’s Committee for Medicinal Products for Human Use, or CHMP, adopted a negative opinion for a Conditional Marketing Application for eteplirsen.

Ataluren is a small molecule indicated for the treatment of patients who have DMD resulting from nonsense mutations in the dystrophin gene, which also affect approximately 13% of DMD patients. In 2014, ataluren received conditional

marketing authorization from the European Commission, and has since been approved in several other countries outside of the United States. Ataluren’s indication is currently limited to ambulatory patients five years of age and older. In February 2018, the FDA reiterated its denial of PTC Therapeutics, Inc.’s appeal of the complete response letter for the new drug application for ataluren.

Current best practices for treating DMD patients also dictate a multidisciplinary approach to disease management, which includes physical and occupational therapy to preserve strength, function and flexibility, orthopedic management to reduce the risk of scoliosis and other bone and joint problems, pulmonary, cardiac and gastrointestinal management, and psychosocial management to support behavior and learning.

Burden of disease

Despite recent therapeutic advances, DMD represents a significant societal and economic burden. The economic burden, estimated at $1.2 billion annually in the United States (excluding costly mortality and end-of-life care expenses), includes costs associated with hospital admissions, medication, frequent doctor visits and investment in assistive devices, as well as indirect costs related to productivity losses for the caregivers and costs due to pain, anxiety and social handicap. Of this amount, approximately 45% is represented by indirect costs. Only a small proportion of DMD patients are employed and many caregivers reduce their hours or stop working altogether to care for their children, who progressively require more help with everyday tasks, such as eating, dressing and using the bathroom. In some cases, patients also experience serious mental health issues that require additional support and treatment.

Solid’s 360-degree solution

We aim to address the full spectrum of DMD disease manifestation, from its underlying genetic cause to other disorders that result from disease progression. We are advancing corrective therapies, disease-modifying therapies and assistive devices, as well as tools to accelerate drug development.

Gene transfer—A corrective therapy

Gene therapy is a therapeutic approach that aims to address diseases caused by gene mutations. A gene is a portion of deoxyribonucleic acid, or DNA, that provides the instructions for the body to construct proteins that perform functions needed for life. Genes are prone to mutations, which can either be inherited or occur spontaneously. While many mutations are harmless, some lead to the absence of crucial proteins, resulting in serious genetic diseases like DMD.

Gene transfer, a type of gene therapy, is designed to address diseases caused by mutated genes through the delivery of functional versions of those genes, called transgenes. The transgenes are then utilized by the body to produce proteins that are absent or not functional prior to treatment, potentially offering long-lasting beneficial effects.

We have focused our initial efforts on gene transfer because we believe it has the greatest potential to address the root cause of DMD: the absence or near-absence of dystrophin protein. If successful, we believe gene transfer can slow or stop the progression of DMD in a majority of patients, irrespective of their genetic mutation, by producing long-term, muscle-specific expression of a functional dystrophin-like protein.

Our gene transfer candidate, or vector, includes three components:

SGT-001, our lead gene transfer candidate, is designed to preserve muscle function in DMD patients after a single administration. The SGT-001vector is comprised of a functional transgene and a muscle-specific promoter, which are delivered via an AAV capsid.

The vector is modified to no longer self-replicate, yet retains its ability to effectively introduce new genetic material directly into patients’ cells. AAV vectors have been extensively studied in human clinical trials in multiple disease

indications, including in clinical trials of high-dose, systemically delivered AAV gene therapies being conducted by third parties.

Capsid: The capsid of the SGT-001 vector is derived from a naturally occurring, non-pathogenic virus called AAV. There are several subtypes of AAV capsids that differ based on the proteins that make up their structure. These capsids have affinities for different sites in the body. We selected the AAV9 serotype capsid for clinical development based on our preclinical data, which demonstrated the capsid’s ability to enter skeletal, diaphragm and cardiac muscle tissues, as well as its favorable tolerability reported in other gene transfer clinical programs.

Transgene: Dystrophin, the largest gene in the body, exceeds the carrying capacity of AAV vectors. To overcome this challenge, we advanced development of the SGT-001 transgene, a synthetic, dystrophin-like gene that fits into AAV and has the ability to drive functional protein expression in skeletal, diaphragm and cardiac muscle tissue.

The concept of a modified therapeutic dystrophin gene originated from research on Becker muscular dystrophy, or BMD, where researchers discovered that certain BMD patients had mutations in the dystrophin gene that drove expression of a functional form of dystrophin protein, allowing patients to live relatively normal lives. This discovery led scientists to engineer a number of synthetic, dystrophin transgene constructs, called microdystrophins, that retained only the most critical components of the full-size dystrophin gene yet were small enough to fit within AAV packaging constraints. There are several types of microdystrophins that differ based on the configuration of their components. Microdystrophins were subsequently demonstrated to functionally protect muscle in mouse models of DMD.

The SGT-001 microdystrophin construct, which is our lead clinical candidate for DMD, is based on three decades of development and optimization work at the University of Missouri and the University of Washington as well as other academic institutions. In preclinical studies, Jeffrey Chamberlain, Ph.D., from the University of Washington, and Dongsheng Duan, Ph.D., from the University of Missouri, identified a proprietary configuration of genetic components that, when administered systemically, produces functional microdystrophin protein expression that not only stabilizes muscle membranes and protects muscle against injury, but also simultaneously restores the localization of DGC to the muscle membrane, notably increasing neuronal nitric oxide synthase, or nNOS, concentration. In subsequent published studies, Drs. Duan and Chamberlain demonstrated in animal models that, in comparison to earlier configurations, nNOS-restoring microdystrophins were more effective in improving muscle function and resistance to fatigue.

Promoter: The expression of the SGT-001 microdystrophin transgene is regulated by a modified, synthetic muscle-specific promoter cassette called CK8, which is derived from the naturally occurring muscle creatine kinase promoter. Regulatory cassettes, such as CK8, are used to prompt gene expression specifically in muscle tissues. In comparison to other regulatory cassettes, we chose CK8 due to its small size and its ability to drive microdystrophin transgene expression in skeletal, diaphragm and cardiac muscle tissues. In our preclinical studies in small and large animal models, CK8 restricted microdystrophin transgene expression to these muscles.