Pharmaceutical formulations comprising human insulin, human C-peptide, and human proinsulin

DETAILED DESCRIPTION OF THE INVENTION The three essential constituents of the pharmaceutical compositions of this invention and administered in accordance with the method of this invention are human insulin, human C-peptide, and human proinsulin.
The administration of a combination of human insulin, human C-peptide, and human proinsulin using a composition in accordance with this invention will produce a more natural utilization of glucose and better glucose control than is achieved by insulin alone, thereby diminishing hereinbefore described adverse diabetic complications.
Human proinsulin is available via a variety of routes, including organic synthesis, isolation from human pancreas by conventional methodology, and, more recently, recombinant DNA methodology.
In broad outline, the production of proinsulin using recombinant DNA methodology involves obtaining, whether by isolation, construction, or a combination of both, a sequence of DNA coding for the amino acid sequence of human proinsulin.
The human proinsulin DNA then is inserted in reading phase into a suitable cloning and expression vehicle.
The vehicle is used to transform a suitable microorganism after which the transformed microorganism is subjected to fermentation conditions leading to (a) the production of additional copies of the proinsulin gene-containing vector and (b) the expression of proinsulin or a proinsulin precursor product.
In the event the expression product is a proinsulin precursor, it generally will comprise the human proinsulin amino acid sequence joined at its amino terminal end to a fragment of a protein normally expressed in the gene sequence into which the proinsulin gene has been inserted.
The proinsulin amino acid sequence is joined to the protein fragment through a specifically cleavable site, typically methionine.
This product is customarily referred to as a fused gene product.
The proinsulin amino acid sequence is cleaved from the fused gene product using cyanogene bromide after which the cysteine sulfhydryl moieties of the proinsulin amino acid sequence are stabilized by conversion to their corresponding S-sulfonates