Non-clinical studies

• Netazepide (formerly YF476) is a potent, highly selective, insurmountable and orally-active gastrin blocker¹⁸.
• Netazepide blocks the effects of hypergastrinaemia in many different animal models¹⁹. For example, netazepide prevented growth of ECL cells in rats caused by hypergastrinaemia induced by high-dose PPI treatment²⁰. Also, netazepide substantially reduced the incidence of ECL tumours in an animal model exhibiting  hypergastrinaemia secondary to hypoacidity²¹.

Studies in healthy subjects

• Single doses of netazepide caused dose-dependent increases in gastric pH of long duration²², and dose-dependent inhibition of pentagastrin-induced gastric acid secretion²³ (Figure 5).
• Repeated doses of netazepide were as effective as a PPI in blocking pentagastrin-induced gastric acid secretion²⁴ (Figure 6A).
• Netazepide in combination with a PPI suppressed pentagastrin-induced gastric acid more than either treatment alone (Figure 6A). Furthermore, netazepide prevented the increase in plasma chromogranin A (CgA; a biomarker of ECL-cell growth) resulting from hypergastrinaemia induced by PPI alone²⁴ (Figure 6B).
• Netazepide has been well tolerated and safe in over 220 healthy subjects.

Figure 5. Mean (n=10; sd) amount of acid in the stomach before (baseline) and during a 2-h intravenous infusion of pentagastrin in fasting healthy subjects given single doses of netazepide or placebo * p < 0.05

Figure 6. Mean amount of (A). Gastric acid (µmol/min); and (B). Plasma chromogranin A (CgA; U/L), a biomarker of ECL growth, in fasting healthy subjects given a 2-h intravenous infusion of pentagastrin before and after 6 weeks’ treatment with netazepide, a PPI, or both in combination (n=10 per treatment) * p< 0.05 and ** p< 0.01

Netazepide is a designated orphan drug for treatment of g-NETs in Europe and the USA. A search of cancer registries and the literature produced a prevalence for g-NETs of 0.32 (range 0.1–0.9) per 10,000 people in 10 European countries and 0.3 per 10,000 people in the USA. However, those values are probably under-estimates because g-NETs are under-reported²⁵. 80% of g-NETs are found in CAG patients.

We tested netazepide in open studies in patients with CAG, hypoacidity, hypergastrinaemia, multiple g-NETs and raised plasma CgA. Netazepide once daily for 12 weeks in 16 patients in two centres reduced the number of tumours and size of the largest one (Figure 7), eradicated all tumours in one patient, and normalised CgA in blood. The changes partially reversed over the 12 week recovery period²⁶.

Figure 7. Size of the largest tumour in two representative patients with CAG and g-NETs, before and after 12 weeks’ netazepide

After an average of 14 months off netazepide, 13 of the 16 patients took it for another 52 weeks. While off treatment , the number of tumours (Figure 8A), the size of the largest tumour (Figure 8B), and CgA had all increased significantly (Figure 8C), and gastrin levels remained high (Figure 8D). Treatment with netazepide for 52 weeks eradicated all tumours in 5 patients, left one patient with only one tumour, reduced the number and size of tumours in the other patients, and normalised CgA in blood. Gastrin in blood did not increase further during dosing (Figure 9). Netazepide was well-tolerated and safe⁹.

Figure 8. Changes in patients with CAG and g-NETs during time off netazepide (mean 14 months, range 8–19 months). *p˂0.05; **p˂0.01; ***p˂0.001. B1 = end of 12 weeks’ netazepide. B2 = start of 52 weeks’ netazepide.

Figure 9. Effect of netazepide for 52 weeks in 13 patients with CAG, hypergastrinaemia, raised plasma CgA in blood, and multiple g-NETs

** p = <0.01;  *** p = <0.001

One of the centres also measured gene expression in mucosal biopsies and miR-222 in blood samples taken from 8 of the patients, and compared the results with those from a group of 10 normogastric healthy controls who had a normal stomach at endoscopy.

• Netazepide reduced mucosal gene expression of CgA, histidine decarboxylase (HDC), pappalysin 2 (PAPPA 2), endoplasmic reticulum protein (ERP), eosinophil phospholipase (CLC), and secretogranin 2 (SCG 2).  In contrast, it increased expression of claudin 10 (CLDN10)¹² which modulates tight junction permeability ^13,14 (Figure 10). CLDN10 increases during successful cancer therapy.
• miR-222 expression was higher at baseline in mucosa and serum of patients compared with healthy controls; it decreased significantly during netazepide treatment and returned to baseline after treated ceased¹³ (Figure 11). miR-222 reduces the tumour suppressor activity of p27^kip1

.

 Figure 10. Mean (sd) miR-222 expression in the stomach lining and blood of patients with g-NETs (n=8) before and after 12 months’ netazepide compared with healthy subjects (n=10).  *P< 0.01 and ***P<0.0001

Figure 11. Expression of gene biomarkers in samples of the stomach lining of g-NETs patients (n = 8) before and after 12 months’ netazepide.   * p =<0.05 and ** p=<0.01

Five patients continued taking netazepide, on a named patient basis, for up to 4.5 years. Time to eradication of all tumours depended on the number of tumours. All tumours were eradicated within a year in patients who had up to 6 tumours. Larger numbers of tumours took much longer (Figure 12), which is not surprising given that the stomach lining of CAG patients is atrophic.

Figure 12. Long-term netazepide 25 mg once daily can eradicate multiple g-NETs in CAG patients (unpublished)

In CAG patients with g-NETs, netazepide once daily by mouth:

• can eradicate all tumours, if patients are dosed long enough;
• must be given continuously otherwise tumours regrow;
• reduces expression of biomarkers CgA and miR-222 in blood, and modulates the expression of several genes in the gastric mucosa, including increasing expression of claudin 10;
• can be monitored by measuring biomarkers CgA and miR-222 in blood, avoiding the need for regular gastroscopy;
• is a novel targeted medical treatment, and an alternative to surgical removal of the tumours;
• is safe and well tolerated; and
• merits a multicentre, placebo-controlled trial.

In summary, netazepide can eradicate all g-NETs if patients are dosed for long enough. More importantly, the normalisation of gene expression, in particular the increase in claudin 10 in cells in the gastric mucosa, and normalisation of biomarkers CgA and miR-222 in blood probably reduce the potential of cells to metastasise and to develop into gastric cancer. That benefit starts long before the tumours are eradicated.