1 TABLE OF CONTENTS PWS Community Response Letter to FDA ..................................................................................................... 3 References ...................................................................................................................................................... 8 Impact of COVID on PWS Families – A survey in the Global PWS Registry ................................................... 9 Sign-On Background .....................................................................................................................................10 Sign-On Survey .............................................................................................................................................11 Comments from the PWS Community .........................................................................................................12 DESTINY-PWS Principal Investigators .....................................................................................................12 Parents and Caregivers of Individuals who identified as DESTINY-PWS Trial Participants ..................13 Parents and Caregivers of Individuals in the US ......................................................................................16 Parents and Caregivers of Individuals Outside the US .............................................................................56 Signatures .....................................................................................................................................................70 Parents and Caregivers of Individuals with PWS in the US ......................................................................70 Parents and Caregivers of People with PWS Outside the US ..................................................................76 Individuals with PWS in the US ................................................................................................................81 Individuals with PWS Outside the US.......................................................................................................81 Researchers and Scientists .......................................................................................................................82 Healthcare Providers ................................................................................................................................82 Other Supporters .....................................................................................................................................85 2 PWS Community Response Letter to FDA April 7, 2021 Re: Request for Regulatory Flexibility & Review of NDA for DCCR, a Potential Treatment for Prader-Willi Syndrome; Unique Impact of COVID-19 on Prader-Willi Syndrome Clinical Trials Dear FDA Leadership, We represent the Foundation for Prader-Willi Research (FPWR) and the Prader-Willi Syndrome Association | USA (PWSA|USA), two patient advocacy groups that support thousands of individuals with Prader-Willi syndrome (PWS) and their families. We are writing on behalf of the patient community to bring to your attention a recent decision by FDA regarding a potential new therapy for PWS, and to request further dialogue and consideration. Specifically, the decision by the FDA advising Soleno Therapeutics that additional efficacy trial(s) for DCCR (diazoxide choline extended release) are needed prior to an NDA submission has raised concern that access to this promising therapeutic will be unnecessarily delayed. We are asking the FDA to reconsider in light of the unprecedented circumstances of the past year. More broadly, we appreciate that the FDA has a long-standing policy to exercise regulatory flexibility, and a history of doing so in rare disease; however, we propose that the full potential of regulatory flexibility to efficiently advance orphan product development in PWS has not been realized. We are asking for additional dialogue to convey the unique challenges of PWS clinical trials and to collaboratively work with the Agency to find solutions for Soleno’s product as well as other clinical packages before the Agency. PWS is a rare neurodevelopmental and metabolic disorder caused by loss/inactivation of a contiguous set of imprinted genes on chromosome 15. Clinically, PWS is characterized as a constellation of symptoms including multiple endocrine deficiencies, a challenging behavioral phenotype, hyperphagia, and, in environments where food is not strictly controlled, morbid obesity. PWS is associated with increased mortality compared to the typical population, with a median age of death of 29 in the largest study to date (1). Common causes of death include complications of obesity (respiratory failure, cardiac issues), hyperphagia-related accidents (e.g., getting hit by a vehicle when running away to get food, choking while rushing to eat food), gastric rupture and pulmonary embolism. To keep children and adults with PWS safe and restrict food access, families must create a completely locked down environment, establishing an institution-like environment within the home, leading to a poor quality of life for the person with PWS and the entire family. Currently, there are no FDA approved treatments for PWS-associated hyperphagia. 3 Our community has worked diligently to build resources that address the FDA’s call for patient experience data, demonstrating high disease burden and the need for effective therapies addressing hyperphagia. We have demonstrated through family stories (2), surveys (3), and a more formal, best-worst scaling study (4) that hyperphagia is “the” aspect of PWS that families want addressed through new therapies, followed by other critical behavioral issues such as anxiety and aggression. We have demonstrated the tremendous unmet medical needs of individuals with PWS (2, 3), and the considerable burden of disease, showing that caregiver burden in PWS exceeds that of caregivers for traumatic brain injury and Alzheimer disease (5) and that higher levels of hyperphagia are associated with increased caregiver burden (6). We have also demonstrated that caregivers are willing to accept considerable risk in exchange for modest improvements in hyperphagia (7, 8). In the absence of a ‘cure’, families would welcome treatments that alleviate PWS symptoms. Finally, as suggested by the Agency during a Critical Path Innovation Meeting, we have also solicited input from individuals with PWS, speaking on their own behalf. Although this was challenging (not all individuals are capable of expressing their views), Dr. Elizabeth Dykens and her team elicited opinions from young adults with PWS on treatment preferences and disease burden, which nicely align with that of caregivers (9). This patient experience data is complemented by natural history studies that provide critical information to support clinical trials, including an NIH study funded 2006-2014 (10) as well as an ongoing registry-based prospective study of behavioral changes over time and serious medical events (11). COVID-19 had a profound impact on the conduct and outcome of ongoing PWS clinical trials. Two large Phase 3 clinical trials evaluating new drugs for PWS were underway at height of the first COVID-19 wave of infections and related public health measures (e.g., stay at home orders). Beyond the cross-cutting issues that the clinical trial enterprise faced as a result of the pandemic (e.g., missed/delayed clinic visits), there were unique impacts on the PWS community that, we believe, could have led to confounding of clinical trial data upon the onset of the pandemic in the US (March 2020). PWS is defined by an extremely complex behavioral phenotype, with hyperphagia, anxiety, temper outbursts, rigidity and obsessive-compulsive behaviors interacting in the setting of social cognition and intellectual deficits (12). The primary outcome measure for most PWS clinical trials is the Hyperphagia Questionnaire for Clinical Trials (HQ-CT), a caregiver- reported outcome measure assessing observable hyperphagia behaviors. While we believe this measure is appropriate for the PWS population and it has generally performed well in previous clinical trials, a limitation of the measure is its potential to be impacted by environmental changes. We believe this limitation became insurmountable in the face of the pandemic. Indeed, we have collected data on the impact of the COVID-19 pandemic on the US PWS patient community, with a survey administered through the Global PWS Registry. This survey documented increased caregiver stress, increased anxiety for individuals with PWS, as well as overall changes in food-related behaviors and activity due to COVID, with behaviors changing in sometimes unpredictable ways (13). These findings are corroborated by a similar study of PWS families in Europe (14). While the uncertainty and unexpected changes to routine that were experienced across the US had a profound impact on everyone, the particular sensitivity and inability of individuals with PWS to cope with unexpected change is well documented and would be expected to negatively impact the consistency and reliability of a measure such as HQ-CT. In a Phase 3 trial by Soleno Therapeutics, pre-COVID data showed significant improvements in HQ-CT scores; families reported positive outcomes with continued improvement in the open label extension. Publicly released data from Soleno Therapeutics demonstrated that PWS participants receiving DCCR showed a drop in HQ-CT scores. While the reduction in HQ-CT scores