* Any views expressed in this opinion piece are those of the author and not of Thomson Reuters Foundation.
Whatever the exact numbers, few would dispute that only a small fraction of health R&D funding targets conditions in poor countries that account for most of the global disease burden.
This is hardly surprising, given that markets in these countries have historically been unable to deliver sufficient financial returns to support the commercial development of health solutions for neglected diseases.
To help meet the most urgent health needs of developing countries, the Bill & Melinda Gates Foundation is employing a range of innovative financing strategies that we believe can help markets ease the bottlenecks at various stages of the discovery, development, and delivery lifecycle of new medical products.
For example, equity investments can advance early-stage discovery andinnovation; commercialisation loans are an efficient way to scale-up manufacturing; and volume guarantees and delivery investment funds can help pharmaceutical companies and health care providers to get important vaccines and drugs to the people who need them.
While public-private partnerships are not uncommon in global development, there is a big opportunity to leverage novel financial strategies — alongside traditional grants, partnerships, and advocacy efforts — to stimulate private-sector R&D, encourage market-driven efficiencies, and attract new capital.
This is important for two reasons. First, the private sector has enormous untapped capacity to help solve health problems in poor countries through innovative technology platforms; efficient manufacturing processes; the ability to validate business models and the viability of commercial products; and access to capital resources such as equipment and manufacturing plants.
Second, there is much the private sector can gain from working with institutions such as ours in developing economies: the ability to test new product concepts, a better understanding of regulatory and delivery requirements in developing countries, and access to large potential markets.
One of the areas we are most excited about is helping youngbiotechnology companies advance early-stage development of potentially ground-breaking health solutions such as drugs and vaccines. Because the foundation's investment activity is driven by charitable rather than financial goals, we can invest strategically in this high-risk period in product development.
Two years ago, for example, we made a US$10 million investment in Liquidia Technologies, whose nanotechnology-based product development platform could revolutionise the development of safer and more effective vaccines and medicines. Liquidia's approach allows for quick, precise and cost-effective design and fabrication of scalable particle-based vaccines and therapeutics.
Last fall, we finalised a US$6 million investment in Atreca, a start-up company that has developed technology to help researchers rapidly identify the antibodies produced by humans in response to different diseases. This knowledge can, in turn, be used to accelerate the development of antibody-based vaccines, therapeutics, and diagnostics for infectious diseases such as HIV, malaria and tuberculosis (TB).
We also invested in Genocea Biosciences, a biotech company working on technology to quickly identify immune cell antigens that induce broader and more powerful immune responses than existing vaccine antigens.
But early-stage discovery is only one piece of the puzzle. Our investment earlier this year in Alere Inc. is an example of our efforts to jump-start commercialisation of vital products for the developing world.
Alere is developing easy-to-use and cost-effective diagnostic tools that will rapidly and accurately test for TB and HIV — improving on current laboratory-based technologies and helping to fight the spread of drug-resistant strains of TB. These tools will be available in a compact, battery-powered portable device that can be used in the most basic healthcare settings.
A US$21.6 million grant will fund the development of a new TB diagnostic. And US$20.6 million in loans at below-market interest rates will help finance the expansion of Alere's manufacturing facilities in Germany, in exchange for a commitment to make its TB and HIV diagnostic products available at affordable prices in developing countries.
But creating the right market incentives is only part of the challenge — getting affordable and effective health solutions and services to the people who need them can also be difficult.
Uncertainty and inefficiencies in procurement processes often keep costs high and lead to frequent shortages. Volume guarantees are a way to tackle both challenges: they assure manufacturers that a market exists for their products, and, by enabling suppliers to plan for manufacturing and distribution, they lower costs and ensure supplies are stable.
Earlier this year, for example, agreements were announced with Bayer HealthCare and Merck to make long-acting, reversible contraceptive implants available for tens of millions of women in the world's poorest countries at a more than 50 per cent cost reduction. 
We have also committed US$7 million — alongside other investors — to the Africa Health Fund, which invests in private health companies that deliver affordable, high-quality health tools and services to low-income populations across Africa.
The fund is working with the Nairobi Women's Hospital to add new clinics in underserved communities in Western Kenya. And it is financing the expansion of a Kenyan manufacturer of single-use needles into Uganda and Tanzania.
We also are working with the Medical Credit Fund, a not-for-profit venture that makes small loans to help African midwifery and traditional medical clinics improve service delivery and become more sustainable. The clinics also receive business and technical assistance to strengthen operations and basic health practices.
Over the next several years, we expect to increase our investments in these kinds of innovative financing mechanisms. While they may be beyond the comfort zone of other philanthropic organisations, we see their potential to help catalyse the discovery and development of new tools in the fight against diseases in the developing world.
Trevor Mundel is president of the Global Health Division at the Bill & Melinda Gates Foundation.
 Darmstadt et al. Family Planning Taking Its Place on the Global Stage(Bill & Melinda Gates Foundation, 2013)