Parasitology Research

, Volume 111, Issue 1, pp 1–6

From methylene blue to chloroquine: a brief review of the development of an antimalarial therapy

Authors

    • Department of PathologyUniversity of Minnesota School of Medicine
  • Ernst Hempelmann
    • Department of PharmacologyWitwatersrand University
  • Agnieszka Skórska-Stania
    • Department of Crystal Physics and Crystal Chemistry, Faculty of ChemistryJagiellonian University
Review

DOI: 10.1007/s00436-012-2886-x

Cite this article as:
Krafts, K., Hempelmann, E. & Skórska-Stania, A. Parasitol Res (2012) 111: 1. doi:10.1007/s00436-012-2886-x

Abstract

Malarial treatment is widely and readily available today. However, there was a time in the not-so-distant past when malaria was a deadly disease with no known cause or cure. In this article, we trace the origins of an antimalarial therapy from the discovery of the nature of the malarial parasite through the development of chloroquine. We dedicate this article to Johann “Hans” Andersag, the scientist who developed chloroquine, on the 110th anniversary of his birth, 16 February 1902.

Elucidation of the cause of malaria

In 1887, the Polish pathologist Czesław Chęciński applied a combination of methylene blue and eosin to blood smears and discovered the daisy-like and sickle-shaped parasites we now know as Plasmodium malariae and Plasmodium falciparum. Until this time, there were many hypotheses regarding the causative agent of this disease, from poisonous air (a theory mentioned as early as 1476 by Leonardo Bruni (Bruni 1476)) to bacteria (Klebs and Tommasi-Crudeli 1879). Three years after Chęciński’s stain was published, the German physician Ernst Malachowski discovered a method of polychroming methylene blue that, when used in combination with eosin, revealed not only a range of colors within leukocytes, but also the elusive purple-red nucleus of the malarial parasite (Krafts et al. 2011). The discovery of the malarial nucleus provided definitive proof that the malarial organism was a eukaryote. A search for an effective antiparasitic malarial treatment could now begin in earnest.

Paul Ehrlich (1854–1915)

Paul Ehrlich (Fig. 1), a highly renowned German physician and scientist, developed a new and effective stain for blood in 1880 which he termed the neutralen Farbkörper or “neutral stain.” This stain incorporated methylene blue and acid fuchsin and allowed differentiation between the different types of white blood cells. Among his remarkable accomplishments was his discovery that certain dyes could be used as drugs which would kill a specific organism while leaving other tissues unharmed.
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Fig. 1

Paul Ehrlich in 1910

In 1891, Ehrlich discovered that methylene blue fell into this category of “magic bullet” drugs, in this case targeting the malarial organism (Fig. 2). Until this point in time, the primary treatment for malaria was quinine (Fig. 3a), a natural substance derived from the cinchona tree of South America and thus limited in supply. Ehrlich’s introduction of methylene blue (Fig. 3b), a synthetic compound, allowed large-scale production of antimalarial therapy, unlimited by the supply or location of natural resources.
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Fig. 2

Figure from Guttmann and Ehrlich’s 1891 paper “Ueber die Wirkung des Methylenblau bei Malaria” (On the Action of Methylene Blue on Malaria) showing the action of methylene blue on the organism in an infected patient (Guttmann and Ehrlich 1891)

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Fig. 3

Structures of relevant antimalarial drugs. a Quinine. b Methylene blue. c Chloroquine

That same year, Gutmann and Ehrlich successfully treated two patients—a domestic servant and a sailor—with methylene blue (Guttmann and Ehrlich 1891). Ehrlich’s student, Röhl, continued antimalarial trials with methylene blue at Bayer in Eberfield. However, methylene blue was found to be insufficiently effective to supplant quinine as an antimalarial drug. Röhl began testing the company’s antimalarial compounds in birds (Figs. 4 and 5) and devised a new compound in which one methyl group was replaced by an aminoalkyl group. Scientists at Bayer began synthesizing a large number of compounds, the most successful of which was termed quinacrine (subsequently marketed as mecaprine and atabrine), which they synthesized in 1931.
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Fig. 4

Bayer laboratory (Pharmakologisches Labor) (courtesy, Bayer AG Archiv)

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Fig. 5

Testing antimalarial compounds using birds (Pharmakologisches Labor) (Courtesy, Bayer AG Archiv)

Hans Andersag (1902–1955)

Johann “Hans” Andersag (Fig. 6) was born February 16, 1902, in Lana (Meran) to Johann Andersag and Cresienz Andersag (née Tribus) (Fig. 7). Johann, the short form of the name Johannes, is derived from the Hebrew name Yehochanan יוחנן meaning “Yahweh (JHWH) is gracious.” Popular in Northern Europe, especially in Germany, the name Johannes has several variants including, Hans (diminutized to Hänschen or Hänsel), Hannes, Jens, and Jan. Later in his life, Andersag changed his given name from Johann to the shortened form Hans.
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Fig. 6

Hans Andersag (courtesy, Bayer AG Archiv)

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Fig. 7

Birth certificate of Johann “Hans” Andersag, pages 1 and 2. (Courtesy, parish register of Lana a.d.E.). Translation: Parish of Lana: List of the 1902 born and baptized children. Name and first name: ANDERSAG, Johann Josef. Born: 16 February 1902, 10 ½ at night. Baptized 17 February 1902, 1 in the afternoon. Name of the father: Johann Andersag, born in Lana 24. Aug 1861, son of Johann and Anna. Position of the father: Tenant. Name of the mother: Cresienz nee Tribus, born in Tisens 27. Aug. 1866, daughter of Michael and Josefa

Andersag studied chemistry in Munich from 1921 to 1927 and worked at Bayer in Elberfeld until 1955 (Fig. 8). He was married to Else Andersag née Nouvortne.
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Fig. 8

Andersag (left) at Pharmazeutisch-wissenschaftliches Labor, Elberfeld, 6 December 1953 (courtesy, Bayer AG Archiv)

In July, 1934, Andersag modified atabrine by replacing its acridine ring with a quinoline ring. The resulting compound, which would later be termed chloroquine (Fig. 3c), was found to have high antimalarial activity, and unlike methylene blue or atabrine, did not discolor skin and eyes.

Andersag began with two compounds: oxaloacetic acid diethylester and m-chloroaniline (Fig. 9). His process consisted of the following steps (Fig. 10):
  1. 1.

    Condensation of m-chloroaniline with oxaloacetic acid diethylester

     
  2. 2.

    Saponification and thermal decarboxylation

     
  3. 3.

    Reaction with phosphorus oxychloride (POCl3)

     
  4. 4.

    Substitution by a diamino group

     
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Fig. 9

a, b Pages from Andersag’s laboratory notebook detailing his method for the synthesis of chloroquine. (courtesy, Bayer AG Archiv)

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Fig. 10

Synthesis of chloroquine by Andersag

Andersag made a salt of the base using 2,4,-dihydroxybenzoic acid. This salt received the name resochin, being the RESOrcinate of a 4-aminoCHINolin.

Resochin was tested in 1935 by Bayer against blood-induced vivax malaria in four paretics at a psychiatric clinic in Düsseldorf but was found to be “too toxic for practical use in humans” (Coatney 1963). Subsequently, Bayer shelved the drug for more than 10 years, a decision that would come to be known as “the resochin error.”

Meanwhile, Andersag continued to modify the drug to minimize the toxic effect, producing the compound 3-methylresochin (Dünschede 1971). This compound was named “sontochin” and was tested at the Institute for Tropical Diseases in Hamburg. By the end of 1939, over 1,100 patients with malaria had been treated with sontochin.

Both drugs, resochin and sontochin, were patented in November 1939 (Reichspatentamt, Patentschrift Nr 683692) and later issued to The Winthrop Chemical Company through their IG Farben cartel arrangement with Bayer (US Patent 2 233 970). Clinical trials with sontochin were also conducted jointly by French and German scientists in Tunisia in 1941–1943, with very impressive results. In May, 1943, drug supplies and accompanying data were handed over by the French authorities to the Allied Forces. During the following years, resochin was rediscovered; it was given the name “chloroquine” by EK Marshall in November 1945 (Coatney 1963).

Chloroquine was a first-line antimalarial therapy for many years. As is the case for most antimicrobial drugs, resistant strains of the target organism eventually developed. However, since the mechanism of the drug (inhibition of hemozoin biocrystallization) involves a host-derived drug target (which cannot be modified by the malarial parasite), it took over 20 years for resistant forms of malaria to develop (Hempelmann 2007). For those 20 years, Andersag’s drug saved countless lives and it continues to be an effective antimalarial treatment nearly 80 years later.

Copyright information

© Springer-Verlag 2012