Pigs and rabbits will help produce a pulmonary surfactant on a commercial scale. This is an essential substance in treating a sickness that affects thousands of premature babies in this country and causes many deaths, namely, Respiratory Distress Syndrome (RDS). Researchers at the School of Medicine of the University of São Paulo (FM-USP) have already achieved good results by applying a surfactant extracted from the lungs of pigs and produced by the Butantan Institute in premature rabbits.
Produced naturally by the lungs, the surfactant acts inside the alveoli (microscopic sacs where the exchange of oxygen and carbon dioxide takes place), enabling them to stay open during expiration. RDS, caused by an insufficiency of surfactant produced by the lungs is one of the main pathologies in premature babies. The shorter the pregnancy, the greater is the pulmonary immaturity and the higher the incidence of RDS; around 50% of the so-called extremely premature babies, those born at between six and a half and seven months (from the 26th to the 28th week), suffer from it. But many of those born between the 28th and 31st week are also affected. In 2000, RDS accounted for 7,715 hospital stays and 2,664 deaths of premature babies, according to the Information Technology Department of the Single Health System (DataSUS).
Treatment of RDS consists of the artificial replacement of the surfactant during the first hours of the baby’s life directly in the trachea. The surfactant is imported, at prices ranging from R$ 900 to R$ 1,200 per ampoule, which makes the treatment very costly for the public health system. In each case, up to two ampoules of the medication can be used depending on the seriousness of the illness and the baby’s body mass.
The promise of a Brazilian solution lies in extracting the surfactant from the lungs of pigs, which, like other mammals, are an important source of the substance. The research project recently completed by the pediatrician Celso Moura Rebello, of the FM-USP goes in the same direction.
Rebello and his team measured the effects of the surfactant of pig origin manufactured experimentally at the Butantan Institute in premature rabbits. The results were compared with those obtained using one of the most commonly sold surfactants produced using bovine lungs. Before developing the methodology, Rebello underwent training for two years at the University of California, in Los Angeles (USA), under the advise of Alan Jobe and Machiko Ikegami, international references in the field of premature lungs. The project was developed in the Experimental Research Laboratory of the Pediatrics Department of the FM-USP. Rebello compared three features of the mechanical operation of the lungs; the pressure borne during mechanical ventilation, the volume of air, and the expansion capacity of the lung.
Ninety-three baby rabbits, divided into four groups, were studied; 21 of them were given the commercial product; 22 the surfactant produced at Butantan; 25 the natural surfactant extracted from rabbits; and the remaining 25 formed a control group, and were given no therapy. All the animals were born by caesarian section on the 27th day of pregnancy, in order to simulate conditions comparable to those of an extremely premature baby. The animals were anesthetized and connected to a mechanical ventilation apparatus for 20 minutes, through a small incision in the trachea.
The animals’ progress supplied data, which was analyzed by a computer program developed by the Experimental Pulmonary Sector of the FM-USP. The analysis showed that the pressure required for the lungs to receive a given volume of air was 30% less in the group treated with surfactants than in the control group. In addition, in the test to assess the expansion capacity of the lungs, the treated rabbits gave better results. After the mechanical ventilation, some of the animals were assessed as to the volume the lungs could attain under a given pressure. It was observed that the lungs of the rabbits that had been treated with surfactants attained a larger volume.
And, in examination under the microscope, the lungs of the rabbits that had been given no medication had a higher proportion of damaged alveoli than the ones that had been treated. The action of the surfactant was also examined in vitro. “In none of the tests, was there any difference in efficiency between the commercial product and the Butantan surfactant”, emphasizes the researcher, the research data were presented to the Brazilian Perinatology Congress, held from November 10 to 14, 2001 in Florianópolis (SC).
Before beginning commercial scale production, Butantan needs to register the product with the Ministry of Health’s National Sanitary Inspection Agency (Anvisa), which is responsible for inspecting medications. To do this, it is essential that a clinical trial of the Brazilian surfactant be carried out in human beings to prove that it is efficient.
With this goal in mind, Rebello is preparing a study set to begin in August 2002 and to last for around two years. The work will be submitted to the National Child Health and Human Development Institute of the United States. It will involve around 360 premature babies and nine university hospitals – five in the city of São Paulo, three in the state interior and one in Porto Alegre (RS). Professor Isaías Raw, coordinator of the Biotechnology Center at Butantan, the institute that has been developing the production of a local surfactant since 1997, reminds us that “the clinical trial is the most complicated step before beginning production of the surfactant on an industrial scale”. He estimates that investment of around R$1 million will be needed to complete this stage. The others – bench studies and technological development of production batches of the product with sufficient quality for testing in human beings – have already been successfully completed.
The researchers are confident, since the Butantan surfactant will have a great advantage over any imported competitor, namely, low cost. Raw calculates that the product can be sold by the federal government for distribution through the public health network for between R$125 and R$200 an ampoule, about 15% of the cost of the imported product. One of the reasons for this reduction is the technique used for extracting the surfactant from the pigs’ lungs, which the institute is patenting. This technique, explains Flávia Kubrusly, of the Butantan Biotechnology Center, “replaces the use of high-speed centrifuges for extracting the surfactant with a sort of paper called cellulose DEAE, which is much cheaper when employed on an industrial scale”. There are other reasons for lowering the cost: Butantan undertakes no marketing campaigns and the sale is not designed to make a profit.
With the price reduction, the use of the product should expand the treatment of pulmonary deficiencies in full-term new-born babies – those that are born at the normal time, after 37 weeks of pregnancy – and even children that suffer from serious pneumonia. In this and other sicknesses, such as meconium aspiration syndrome (meconium is the liquidity in the digestive system of the baby itself). Nonetheless, as the dosage is calculated according to the body weight – 100 milligrams per kilogram of baby – this therapy is currently very expensive. “In children and adults, the present cost is prohibitive. Making the medication cheaper would increase the chances of being able to use it to treat these illnesses”, says Rebello.
Besides the economic potential for the government and the increased use of the medication, there are other benefits associated with local production. For the public university, it is the learning of how to carry out the so-called multi-center clinical trials, a technique that, according to a Rebello, has been dominated mainly by pharmaceutical companies. There is also the acquisition of technological competence to be applied to other products. Furthermore, the production will include differentiated surfactants, such as the freeze dried type, an innovation adopted by Butantan.
Raw says that the technique developed for the production is a real discovery. “The technology employed proved to be so good that with one small plant like the one we have, we can meet the needs of Brazilian surfactant consumption”. This need, according to Flávia Kubrusly, is around 180,000 doses – equivalent to 22,500 ampoules -, to treat premature babies affected by RDS, a number put at around 45,000 babies a year.
A precious liquid
The pulmonary alveoli are microscopic sacs, which the air we breathe reaches in the end of the process, there the oxygen taken in is absorbed and enters the blood stream through the capillaries and is exchanged for carbon dioxide, which is exhaled. The pulmonary surfactant is a liquid that acts as a sort of natural detergent, to keep the alveoli appropriately viscous to be able carry out their task. It is a viscous liquid (it has about 90% lipids in its composition, light in color (between white and pale yellow).
As the internal walls of the alveoli are covered by a very thin layer of water, these sacs close when they empty during exhalation, because of the strength of the attraction between the water molecules. The surfactants reduce this force, preventing the internal walls of the alveoli from sticking together during exhalation.
Produced continuously, by specialized cells in the alveoli – known as type 2 pneumocytes – the surfactant is made up of four types of protein (SPA, SPB, SPC and SPD), as well as phospholipids (compounds of fats and phosphate). In the absence of this natural detergent in sufficient quantity, respiratory distress syndrome (RDS) occurs. This insufficiency arises when the baby is born prematurely and, consequently, the lungs are premature too. For this reason, respiration becomes very difficult and, if the problem is not treated with a surfactant, the baby may die for want of breath.
The researcher explains: “It is possible to detect surfactant in the human lung at the 24th week of pregnancy. Its production gradually increases and reaches its maximum amount per kilogram of body weight in a full term pregnancy at the 40th week. Before the 36th week, production is still small; therefore, if birth occurs prematurely (by definition a premature birth has not completed 37 weeks), this insufficient production of surfactant may lead to RDS. Naturally the more premature the birth, particularly extremely premature, as we have said – the more serious will the RDS be, and it may cause the death of the premature baby”.
In Vivo and in Vitro Assessment of the Function of a New Pulmonary Surfactant of Porcine Origin, Developed and Produced with National Technology (nº 98/14482-5); Modality Regular line of research support; Coordinator Celso Moura Rebello – USP’s Faculty of Medicine; Investment R$ 130,257.72 and US$ 145,147.29