Louise Pearce (March 5, 1885 – August 10, 1959) was an American pathologist at the Rockefeller Institute who helped develop a treatment for African sleeping sickness (trypanosomiasis).

[2][3] Sleeping sickness was a fatal epidemic which had devastated areas of Africa, killing two-thirds of the population of the Uganda protectorate between 1900 and 1906 alone.

[4] With chemists Walter Abraham Jacobs and Michael Heidelberger and pathologist Wade Hampton Brown, Pearce worked to develop and test arsenic-based drugs for its treatment.

In 1920, Louise Pearce traveled to the Belgian Congo where she designed and carried out a drug testing protocol for human trials to establish tryparsamide's safety, effectiveness, and optimum dosage.

The temperature – a very important point – is elevated, rising in the evenings to 101° or 102°F, falling to subnormal in the morning, the range often extending over four degrees or more, and the pulse of very low tension is accelerated, varying from 90 to 130 beats per minute.

These two symptoms are of the greatest diagnostic importance in the early recognition of the disease... Drowsiness, which has gradually been increasing, now passes on to coma, from which the patients can only be roused with difficulty; the temperature falls to subnormal, in rare cases convulsive fits appear, and the patient dies in a complete state of coma.

[4][10]By 1903, researchers had determined that sleeping sickness was caused by a trypanosome, a parasite that lived and multiplied extracellularly in the blood and tissue fluids of its human hosts.

Building on the work of Paul Ehrlich in Germany, who had developed an arsenic-derived drug called Salvarsan for the treatment for syphilis, chemist Walter A. Jacobs and immunologist Michael Heidelberger synthesized 243 possible arsenicals, varying methyl groups, amides, and complex side chains.

In mice and rats the parasites tended to remain in the bloodstream, while in rabbits they invaded the central nervous system, a more comparable model to what happened in humans.

The most successful of the possibilities was tryparsamide, a derivative of atoxyl, in which a carboxyl group was converted into an amide to reduce toxicity of the drug.

[12][13][14][15] The Rockefeller Institute sent Louise Pearce to Léopoldville in the Belgian Congo in 1920 to test tryparsamide, "trusting her vigorous personality to carry out an assignment none too easy for a woman physician and not without its dangers".

[5][16] There she worked with a local hospital and laboratory to design and carry out a drug testing protocol for human trials to establish tryparsamide's safety, effectiveness, and optimum dosage.

Almost all early cases of the previously fatal disease were successfully treated, and most patients, even in the later stages of sleeping sickness, could be saved.

Human trials also revealed that a side effect of other arsenical compounds, damage to the optic nerve and loss of vision, could occur with high or repeated doses of tryparsamide.

[1][5] Observations of differences in tumor development led Brown to research the relationships between bodily constitution (the basic health of an organism) and liability to disease.

[5] After Brown's death in 1942, Pearce reduced the size of the colony, narrowed the scope of the investigation, and began to organize and report on the huge amounts of data that had been collected, including (but not limited to) information on early senescence, achondroplasia, osteopetrosis, eye defects, cystic disease, and hydrocephalus.