Formulation development and manufacturing of a gastrin/CCK-2 receptor targeting peptide as an intermediate drug product for a clinical imaging study

A DOTA-gastrin analogue (APH070) which, when labelled with 111In, has high affinity for the gastrin/CCK-2 receptor (3 nM) and low tumour to kidney ratio in animal models, has been formulated and manufactured for a clinical study. Oxidation of the peptide methionine residue greatly reduces receptor affinity, therefore development work focused on producing a stable intermediate drug product (iDP) whilst ensuring that the formulation, container, closure and manufacturing process did not inhibit the extremely sensitive radiolabelling reaction (itself a source of oxidation). Stress testing revealed that APH070 was stable at 2–8 °C at pH 6–9. Addition of an antioxidant (monothioglycerol) to the peptide formulation reduced stability when compared to buffer alone. Use of FluroTec (4023/50) stoppers (rather than FluroTec Plus (4110/40)) increased both the stability and radiolabelling efficiency of APH070. Long term stability (6 months) of the final formulation (1 mg/ml APH070 in 0.01 M pH 7.2 phosphate buffer) stored at 5 °C in type I glass vials with FluroTec (4023/50) stoppers was 98.6 ± 0.2% and 98.4 ± 0.1% for upright and inverted samples, respectively. Clinical scale radiolabelling of the final formulation routinely achieves the specification of >85% 111In-APH070 (unoxidised) stable for up to 2 h after dilution with 0.9% w/v saline solution. Specific uptake of the radiopharmaceutical in CCK-2R-expressing AR42J tumours in nude mice has been demonstrated.