Biosynthetic corneas formulated with recombinant collagen restore vision and nerve growth

San Francisco, California – August 25, 2010 – FibroGen, Inc., today announced results of a 2-year clinical study demonstrating that surgical implantation of biosynthetic corneas formulated with the company's proprietary recombinant human type III collagen (rhCIII) restored vision and promoted nerve regeneration (restoring sensitivity) in patients who had corneal damage and significant vision loss. The results of this phase 1, investigator-sponsored study were published today in Science Translational Medicine.1

Corneal damage and disease are major causes of blindness worldwide. In countries where tissue banking is available, such as the US, treatment is by implantation of human donor corneas. However, there is a severe shortage of human donor tissue worldwide. Patients who do receive donor human corneas, however, can still suffer complications, such as tissue rejection. Corneal prostheses, made from synthetic plastics are used in limited cases, but only where human donor grafts are contraindicated or have been repeatedly unsuccessful. These synthetic alternatives are not designed to replace donor tissues or promote tissue regeneration.

FibroGen pioneered the development of recombinant collagen production technology and is the only producer of rhCIII. Since 2005, FibroGen has collaborated with Dr. May Griffith of Linköping University, senior author of today's publication, to develop biosynthetic corneas molded from chemically cross-linked rhCIII. The biosynthetic implants are designed to mimic the human cornea, which is composed mainly of the protein collagen.

"Recombinant human collagen is a viable replacement for naturally occurring human collagen that does not have the limitations of human donor tissue or animal-sourced collagens, such as risk of disease transmission and availability of donor supply," said Dr. Griffith. "Our study provides proof-of-concept that corneal implants composed of recombinant human collagen can promote tissue regrowth and restore vision."

"These clinical results suggest that our collagen could potentially provide an important option for patients by reducing risk of disease transmission and increasing supply of corneal implant material in the face of the worldwide shortage of human donor corneas," said Thomas B. Neff, Chief Executive Officer of FibroGen. "This product concept continues to be improved and additional studies are planned."

In the clinical study, 10 patients with corneal disease underwent resection, followed by surgical implantation with rhCIII-based biosynthetic corneas. Two-year post-surgery results demonstrated that 100% of the transplanted corneas remain viable at two years, cells from the patients' own corneas had grown into the implant, and nerves that had been severed during surgery regrew. In addition, the blink reflex and tear film were restored. In terms of visual acuity, at 24 months, best spectacle-corrected visual acuity improved in six patients, remained unchanged in two patients and decreased in two. None of the patients experienced any rejection reaction or required long-term immunosuppressive therapy, serious issues associated with the use of human donor tissue.

Unmet medical need for a biosynthetic corneal implant

Loss of vision due to corneal disease or trauma affects over 10 million individuals worldwide, but lack of access to good quality donor tissue severely limits the number of transplant procedures that can be done, particularly in the developing world. In the US, an estimated 42,000 corneal grafts are performed annually using optical tissue from cadavers; however, graft rejection can occur, and failure rates are significant. In addition, the mandatory use of steroids with cadaver-sourced corneal material limits their successful use to certain patient populations. Fully synthetic prostheses (without biological activity) have been developed, but their use has been limited to cases where human donor tissue fails repeatedly or cannot be used. Moreover, apart from the US, in most countries, tissue donation and banking systems do not exist.

FibroGen is the only producer of highly purified, fully characterized recombinant human type III collagen (rhCIII) intended to replace similar animal- or human-derived materials currently used in a variety of medical, pharmaceutical, and consumer applications. FibroGen uses proprietary recombinant methodology in a yeast expression system with human DNA sequences to develop synthetic versions of human collagens essentially identical to the native protein. Mixtures of various collagen types found in animal-sourced collagen are nearly impossible to segregate. FibroGen has been able to produce specific types of recombinant human collagen (e.g., types I or III) consistently and reproducibly. FibroGen has developed simple, scalable purification processes that provide highly purified and reproducible lots of protein in any desired quantity, and employs a series of rigorous analytical tests to ensure lot-to-lot consistency and high quality.

About FibroGen

FibroGen, Inc. is a biotechnology-based drug discovery and development company using its expertise in the fields of tissue fibrosis, connective tissue growth factor (CTGF), and hypoxia-inducible factor (HIF) biology to discover, develop, and commercialize novel therapeutics for fibrotic disorders, diabetic complications, anemia, conditions associated with tissue damage or injury, cancer, and other areas of unmet medical need. FibroGen also develops and produces recombinant human collagens and gelatins using unique production technology that provides the basis for FibroGen's proprietary cosmetic dermal filler and biomaterials supply business.

For more information about FibroGen, Inc., please visit www.fibrogen.com.

Reference

1Fagerholm P, et al., A Biosynthetic Alternative to Human Donor Tissue for Inducing Corneal Regeneration: 24-Month Follow-up of a Phase 1 Clinical Study. Science Translational Medicine Volume 2 (25 August 2010).