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Human insulin to rule the roost

Porcine insulin is pure and causes no allergy. Yet, patients will prefer human insulin as it is structurally similar to that produced in our body and costs the same.

Shifting from animal to human insulin has to be done only under medical supervision.

THE NEW Year has brought its share of sweet tidings for millions of diabetics in India. Biosynthetic human insulin that till recently was prohibitively costly and beyond the reach of many has been brought at par with porcine (pig) derived insulin (Rs145 for 10 ml vial).

It is one of those rare instances of patients having the cake and eating it too. Cost parity apart, the single most advantage of using human insulin is the identical amino acid sequence to naturally produced insulin.

Human insulin is so called not because it is extracted from the human body but because it is structurally (and chromatographically) identical to insulin produced by our body. It is produced using recombinant technology using either E. Coli bacteria or yeast.

Human insulin is in fact the first of the biogenetically engineered products ever to be produced in the world. "And the credit goes to Eli Lilly to have produced this recombinant DNA product," said Rajiv Gulati, Chairman and Managing Director, Eli Lilly and Company (India) Pvt Ltd. It achieved this remarkable feat as early as 1981. Nova Nordisk, another manufacturer of human insulin, has also announced a drastic price cut. Eli Lilly has started manufacturing human insulin in India.

The recombinant technology put to rest the worst fear that the insulin production from animals would not be able to cater to the requirement of the ever increasing diabetic population. It was forecasted as early as 1976 that by 1992 demand would outstrip supply. But Eli Lilly's magic proved the doomsayers wrong.

Human Vs animal insulin

One remarkable thing about human insulin apart from the fact that it can be mass-produced is its high level of purity compared to bovine insulin. Animal derived insulin always suffered from an inherent problem of purity. Purity is measured by the presence of non-insulin pancreatic proteins.

The earliest forms were crude concoctions with high levels of impurities. This led to the development of antibodies to insulin in humans that in turn led to altering the time course of action, insulin allergies and insulin resistance. Antibodies form in our body to counter porcine insulin that is a foreign body.

However, porcine insulin now produced has purity comparable to human insulin. This has by far eliminated the problems encountered earlier. "Porcine insulin now available is pure and only a theoretical possibility of antibody formation exists. We don't find much of it in our patients," noted Dr. V. Mohan, Chairman and Managing Director, M.V. Diabetes Specialities Centre (P) Ltd, Chennai.

"Same is the case with allergy. We rarely see it, may be one in a thousand." Similarly with efficacy. Mr. Gulati concurs with Dr. Mohan about the high level of purity with porcine insulin.

The immediate fallout of increased purity level achieved has been a rise in its price. But the high level of purity notwithstanding, the presence of one amino acid (in the case of porcine insulin) not seen in humans cannot be wished away.

This produces a probability of antibody formation in some patients. "Increase in efficacy with human insulin may be seen in these patients. Hence switching over from animal to human insulin should be done under medical supervision," Dr. Mohan stressed.

The thumb rule is to reduce the dosage by 15-20 per cent when changing over. But the chances of maintaining the dosage at reduced level are slim. This is not the case with bovine insulin. The three amino acid difference between bovine and human has a cascading effect on antibody formation and efficacy.

"It is possible that the dosage level reduction will be 30-40 per cent when switching over from bovine to human insulin," Dr. Mohan indicated. Little wonder that bovine insulin costs Rs75 for 10 ml compared to Rs145 in the case of porcine insulin.

"But we still need bovine insulin as the poorest of the poor cannot afford costlier insulin despite its merits," Dr. Mohan averred. But the possibility of diseases like mad cow disease finding its way into humans exists when bovine insulin is used. Similar may be the case with porcine insulin.

Though the cost of porcine and human insulin is the same today, the same may not be the case a few years down the line.

An exodus from porcine to human insulin can be expected sooner than later. This being the case the increased volume vis--vis porcine may bring down the price further.

Lessons to be learnt

"The price of human insulin would only be seen coming down when the number of users increase," said Mr. Gulati. One way for Eli Lilly to bring down the price further is by manufacturing glass vials in India. The neutral grade glass vials are presently imported.

But the real tumbling of prices can be expected when human insulin produced by Indian pharmaceuticals actually hit the market. The sudden and belated price cut is just an indication of things to come.

An industry source does indicate that slashing of human insulin price by the multinational companies was not in keeping the interest of patients but in anticipation of cheaper alternatives by the end of the year from Indian companies.

The price of recombinant hepatitis vaccine plummeting when Indian pharmaceuticals started manufacturing it is still fresh in our memory. Only diamond cuts a diamond. Ask any space or nuclear scientist if you are still not convinced.

R. Prasad

in Chennai

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