Accelerated approval of Oxbryta® (voxelotor): A case study on novel endpoint selection in sickle cell disease

Successes and pitfalls in orphan drug development for sickle cell disease

ABSTRACT

Sickle cell disease (SCD) is a hereditary red cell disorder with a large disease burden at a global level. In the United States and Europe, medicines may qualify for orphan designation (OD), a regulatory status that provides incentives to boost development. We evaluated the development of new therapies for SCD using data for OD granted in the United States and Europe over the last 2 decades (2000-2021). We analyzed their characteristics, pathophysiological targets, trends, and OD sponsors. We then investigated the approval outcomes, including the phase success rate and reasons for discontinuation across different variables. We identified 57 ODs for SCD: 43 (75.4%) small molecules, 32 (56.1%) for oral administration, and 36 (63.1%) for chronic use to prevent SCD complications. At the end of the study (2021), development of 34 of 57 ODs was completed. Four ODs were approved with a success rate of 11.8%. Products targeting upstream causative events of SCD pathophysiology had a 1.8 higher success rate compared with products targeting disease consequences. Large companies showed a fourfold higher success rate compared with small-medium enterprises. Failures in clinical development were mainly seen in phase 3 for a lack of efficacy on vaso-occlusive crisis as the primary study end point, likely related to variable definitions and heterogeneity of pain scoring and treatment. Both advances in SCD knowledge and regulatory incentives paved the way for new therapies for SCD. Our finding of high failure rates in late-stage clinical development signals the need for better early-stage predictive models, also in the context of meaningful clinical end points.

Voxelotor Treatment Providing Transfusion Independence for Patient With Combined Sickle Cell Disease and Lipopolysaccharide-Responsive and Beige-Like Anchor (LRBA) Deficiency

We present a 22-year-old female with transfusion-dependent anemia due to sickle cell disease (SCD) with lipopolysaccharide-responsive and beige-like anchor protein (LRBA) deficiency whose treatment frequency was moderated with voxelotor (Oxbryta®). The patient was transfusion dependent, initially thought to be secondary only to SCD. After the diagnosis of LRBA deficiency, her regimen included abatacept, sirolimus, hydroxyurea, and folic acid, but she still required intermittent transfusion. She was started on voxelotor in January 2020. Since initiation, her baseline hemoglobin level has increased and she is no longer transfusion dependent.

Variation in Endpoints in FDA Medication Approvals: A Review of Acute and Preventive Migraine Medications

BACKGROUND AND OBJECTIVE

To assess the characteristics and extent of variation of the endpoints used in trials supporting the US Food and Drug Administration (FDA) approval of medications treating migraine.

METHODS

Using the Drugs@FDA online database, we identified novel prescription medications approved by the FDA between January 2001 and September 2022, for migraine with or without aura, for both acute and preventive treatment, and for episodic and chronic presentations. For each medication, we used the most recent FDA-approved labeling to identify indication, mechanism of action, mode of administration, manufacturer, approval year, number of pivotal trials, trial design, and primary endpoints.

RESULTS

Sixteen FDA-approved medications for the acute or preventive treatment of migraine were supported by 45 pivotal trials. There were 5 primary endpoint types: (1) change in mean monthly migraine days from baseline; (2) change in mean monthly migraine attacks from baseline; (3) change in mean monthly headache days from baseline; (4) mild to no pain After 2 hours; (5) pain free at 2 hours. There were 3 combinations of coprimary endpoints: (1) Headache Pain Free at 2 Hours and Most Bothersome Symptom Free at 2 Hours; (2) Pain Free at 2 Hours and Sustained Pain Free from 2-24 Hours Postdose; (3) Pain Free at 2 Hours and 2-24 Hours Sustained Pain Free and 2-Hour Pain Relief. Of the 8 preventive migraine medications, the timing of endpoint measurement included the full double-blind period, segments of the double-blind period, and the final month of the double-blind period.

DISCUSSION

Migraine medication trial endpoints were inconsistent within the same indication (episodic or chronic), mechanistic class, and route of administration, frustrating direct comparison among these medications. Furthermore, inconsistent definitions for the indications "episodic" and "chronic" migraine were also observed. Consistent endpoint selection for medications approved for preventive and acute migraine treatment would enhance the ability of patients, physicians, and payers to make informed choices among these medications.

Modulating hemoglobin allostery for treatment of sickle cell disease: current progress and intellectual property

INTRODUCTION

Sickle cell disease (SCD) is a debilitating inherited disorder that affects millions worldwide. Four novel SCD therapeutics have been approved, including the hemoglobin (Hb) modulator Voxelotor.

AREAS COVERED

This review provides an overview of discovery efforts toward modulating Hb allosteric behavior as a treatment for SCD, with a focus on aromatic aldehydes that increase Hb oxygen affinity to prevent the primary pathophysiology of hypoxia-induce erythrocyte sickling.

EXPERT OPINION

The quest to develop small molecules, especially aromatic aldehydes, to modulate Hb allosteric properties for SCD began in the 1970s; however, early promise was dogged by concerns that stalled support for research efforts. Persistent efforts eventually culminated in the discovery of the anti-sickling agent 5-HMF in the 2000s, and reinvigorated interest that led to the discovery of vanillin analogs, including Voxelotor, the first FDA approved Hb modulator for the treatment of SCD. With burgeoning interest in the field of Hb modulation, there is a growing landscape of intellectual property, including drug candidates at various stages of preclinical and clinical investigations. Hb modulators could provide not only the best chance for a highly effective oral therapy for SCD, especially in the under-developed world, but also a way to treat a variety of other human conditions.