Sparrow Pharmaceuticals is an emerging biopharma company on a mission to help patients suffering from an excess of corticosteroids, with a focus on Cushing’s syndrome, autonomous cortisol secretion (ACS), and polymyalgia rheumatica (PMR).
Cushing’s and ACS are both caused by an excess of cortisol produced by tumors. Patients with Cushing’s can present physically with a fatty hump between their shoulders, a rounded face, and pink or purple stretch marks on their skin. Cushing’s syndrome and ACS can both result in high blood pressure, bone loss, type 2 diabetes, weight gain, and mood, cognition, and sleep disorders. Any of those symptoms may be side effects for patients with conditions such as PMR who rely on long-term treatment with corticosteroid medications such as prednisone.
“Cushing’s syndrome impacts around 20,000 patients in the U.S. alone,” says David Katz, Chief Scientific Officer for Sparrow. “Approximately 50% of those patients can be cured by surgery, but some will develop another tumor years later. ACS is an under-recognized condition, but it may affect up to 3 million patients in the U.S. There are also around 2 million people in the U.S. who rely on long-term use of corticosteroid medications to control autoimmune diseases and other conditions.”
The treatments being developed by Sparrow are based on recognition that cortisol and corticosteroid medications are activated in certain tissues such as the liver, bone, fat, and brain, where in excess they act to cause toxicity. The company’s investigational drugs inhibit HSD-1, the enzyme responsible for that activation.
Sparrow is about to launch a Phase 2 trial for Cushing’s syndrome. In early 2022 the company will also begin two additional Phase 2 trials for ACS and PMR, a common autoimmune disease in elderly patients. PMR is an arthritic syndrome characterized by a phenomenon known as claudication, which means the more you use a limb, the more it hurts and the harder it is to use. “For example, the more a PMR patient walks, the more painful and stiff their legs will become,” says Katz. “If they're trying to do anything with their arms, the arms will get stiffer and more painful. The disease is pretty debilitating in terms of physical function. The only approved treatment for PMR is steroids, which have side effects such as diabetes, hypertension, osteoporosis, and fractures.”
Unknown Clinical Challenges
Katz is excited about the clinical trials for ACS and PMR because no sizable interventional trials have been reported in either of those conditions.
“We're going into a completely new area, and we don't know what we're going to encounter in terms of patient recruitment and retention,” says Katz. “There is also no strong precedent for how to get approval for a drug in these conditions. The only treatment indicated for PMR is steroids, and that came without any efficacy clinical trials. There are no drugs approved for ACS. It’s hard to anticipate the challenges we will face when we are in an area that is very new.”
Patient centricity is a topic that is very important to Katz, and he spends a lot of time thinking about how to make trials a more pleasant experience for patients by limiting the burden placed on them. He notes that can sometimes be a difficult trade-off because of the procedures that must be performed to meet regulatory standards.
“In Cushing’s syndrome clinical care and clinical trials, the standard way for someone's cortisol level to be measured is a 24-hour urine collection,” states Katz. “That involves looking at the amount of cortisol in the urine over a 24-hour period. That collection is inconvenient and burdensome, and the patient must then carry it somewhere to be analyzed.”
Sparrow hopes to shift that collection to a spot urine sample, like what patients would experience during a physical. The patient would urinate into a cup and hand it off to a clinic employee for analysis. The process would be much simpler and less burdensome for the patient. Sparrow will first need to prove that in a clinical trial the spot sample will work as well or better than the 24-hour collection. Subjects in the initial clinical trials will have to contribute the 24-hour collections so that Sparrow can demonstrate that future patients will not need to do so.
The Future of Endocrinology
Katz has a positive outlook on the future of endocrinology. Sparrow’s leading drug candidate, SPI-62, is an oral, small-molecule HSD-1 inhibitor. In four clinical trials, it demonstrated potent targeting of HSD-1 in both the brain and liver, and significantly lowered cortisol levels in the liver. The studies also showed a favorable safety and tolerability profile.
“If we are successful at developing SPI-62, I believe it will change the field of endocrinology,” says Katz. “We aim to shift the focus in Cushing’s syndrome to intracellular cortisol as the main driver of symptoms. What I mean by that is if we find that SPI-62 substantially reduces symptoms and that the degree of inhibition of our target HSD-1 correlates well with clinical improvement, then we can get to a new standard of care. We can potentially get rid of the 24-hour urine collections, which will be a big relief to patients. Additionally, many of today's drugs have a side effect called adrenal insufficiency, which results when the drugs either reduce cortisol too much or completely block activity. Many of today's drugs also require frequent monitoring and dose titration to prevent adrenal insufficiency. We believe that with HSD-1 inhibition we might avoid adrenal insufficiency as well.”
Katz is hopeful patients treated with SPI-62 will not require monitoring and dose titration. That proof will take years and lots of clinical trials. Sparrow may also produce the first targeted therapy for ACS. That could improve the recognition of ACS as a prevalent form of hypercortisolism and a substantial cause of morbidity and mortality.
“ACS is probably the most under-recognized condition in endocrinology based on recent epidemiological studies,” adds Katz. “It's possible that as few as 3% of patients who have ACS actually have a diagnosis. That is shocking for a condition that is associated with a lot of cardiometabolic and bone morbidity, negative effects on mood and cognition, sleep, and muscle strength, and is associated with excess mortality. We want to bring attention to this condition by bringing out a targeted therapy to treat a spectrum of symptoms by getting to the root cause of them.”