Clinical evaluation of SMS 201-995. Long-term treatment in gut neuroendocrine tumours, efficacy of oral administration, and possible use in non-tumoural inappropriate TSH hypersecretion.

Long-acting somatostatin analogues such as SMS 201-995 (Sandoz) are being evaluated in a wide range of clinical indications, including gut neuroendocrine tumours and acrogemaly. Long-term continuous SMS 201-995 treatment has achieved useful symptomatic improvement in diarrhoea in 4 patients with metastatic VIPomas who had relapsed following previous treatment. Clinical improvement has outlasted suppression of VIP secretion (suggesting an additional direct antisecretory action of SMS 201-995) and has occurred despite expansion of hepatic metastases. In 6 patients with tumours secreting gastrin and/or glucagon, secretion of these peptides was acutely inhibited by SMS 201-995. However, endocrine and clinical responses to chronic treatment have been less consistent. SMS 201-995 is active orally at doses of 4-8 mg and when given thrice-daily to 6 patients with active acromegaly, suppressed mean 24-h growth hormone levels by 51-88%. Despite significantly reduced plasma insulin concentrations, glucose tolerance did not deteriorate. SMS 201-995 was also effective in suppressing thyroid-stimulating hormone (TSH) and thyroid hormone secretion in a patient with mild thyrotoxicosis due to non-tumoural inappropriate TSH hypersecretion. In all cases SMS 201-995 treatment has been well tolerated and has few side-effects.