THE CONCEALED SIDE OF THE HISTORY OF COMBINATORIAL
Combinatorial chemistry today is an accepted new branch of science that comprises
methods widely applied in drug research and other research fields withinchemistry
and even outside of it. Its beginnings were slow and painfulin the
1980s. The present account describes a story that has not beenheretofore
revealed in the history of its discovery. The format isa conversation
in which Árpád Furka, the original discoverer,provides the
answers to István Hargittai’s questions.
Árpád FURKA*, István HARGITTAI**
*Department of Organic Chemistry, Eötvös Loránd University
H-1518 Budapest 112, PO Box 32
**Institute of General and Analytical Chemistry, Budapest University of Technology
and Economics and Structural Chemistry Research Group of the Hungarian Academy
of Sciences at Eötvös University, H-1521 Budapest, PO Box 91, Hungary
Received: May 14. 2004
Keywords: combinatorial chemistry, split-mix method, peptide synthesis,
How and when did you come to the idea of the combinatorial
Around 1980, I began to think about the possibility of preparing
all membersof families of peptides: dipeptides, tripeptides, tetrapeptides,
or pentapeptides.It was clear from the beginning, that this could be accomplished
only bya new method since a very simple calculation showed that using the
availabletechniques, thousands of years would be needed to synthesize,
for example,all the pentapeptides. Considering the possible solutions, it
was also clearthat multi-component mixtures of peptides could easily be prepared
by usingmixtures of amino acids - instead of the usually applied single ones
- intheir solid phase synthesis.
On the other hand, this did not seem to be an acceptable solution
becauseof the differences in the reactivity of the activated amino acids
that wouldlead to the formation of peptides in significantly different concentrations,
thus causing problems in screening. The goal was to eliminate the problem
stemming from reactivity differences. I solved the problem in 1982,
working in Budapest.
My idea was to make the couplings with single amino acids on equal
samplesof the resin, then mix the samples after coupling. This made it possible
to force the coupling reactions to completion with each amino acid and thus
assuring the equal molar formation of peptides. This is the simple and well-known
split-mix combinatorial synthetic method that reduced the time needed toprepare
the peptide libraries from thousands of years to a few days.
Did you have any idea of how to utilize the peptide mixtures?
Finding the bioactive peptides in a mixture of millions of components
seemedlike finding a needle in a haystack. So a strategy was needed to solve
thisproblem and this strategy (later known as the iteration method) was also
ready in 1982.
Did you try to find applications for the idea?
I discussed the problem of making a patent with a patent attorney
Dr. ÉvaSomfai with whom we worked together in filing other patents
for a Budapestpharmaceutical company. It turned out that patenting would
cost more thanI could afford. The pharmaceutical companies were not interested
in patentingour method. As a safeguard, she suggested to describe the
method ina document and notarize it. This could help in the future in possible
prioritydisputes. I did so and the document was notarized on June 15,
1982.The document can be seen in both the original Hungarian and its English
versionin my home page  and it was also published in Drug Discovery today
When did you first publish the method?
When I discussed the new synthetic method with colleagues I experienced
astrong disbelief. This was the reason why I thought for a long time
about finding the best way of publishing. Finally we published the synthetic
method on posters at two international congresses in 1988: The 14th International
Congress of Biochemistry, Prague  and The 10th International Symposium
of Medicinal Chemistry, Budapest . Although no particular interest orresponse
was forthcoming, in hindsight it was most fortunate that at leastthese Abstracts
about the initiation of combinatorial chemistry had goneon record.
However, the lack of responses by chemists and my failureto find cooperating
biologists quite disappointed me. It took a whilebefore I decided to
submit a manuscript for a full paper.
What was your choice then for your publication?
It was clear to me that it would be impossible to publish the
method in ageneral journal like Nature. So I chose a more specialized periodical,
theInternational Journal of Peptide and Protein Research in which we had
publishedbefore although we knew that the chief editor of the journal had
changedsince that time.
In our experiments we focused on proving that the expected peptides
do formin the synthetic procedure. For this reason only small libraries could
beused. We developed a computer-aided paper electrophoretic procedure 
thatwas successfully used in identifying the components of the synthetic
mixtures. The manuscript, entitled "General method for rapid synthesis of
multi-component peptide mixtures" was sent to Professor Hruby, University
of Arizona, Tucson, and was received on February 12, 1990. The manuscript
was reviewed by three reviewers. One of them, although accepted the paper
with minor revisions, wrote in his comments: "Having spent years endeavoring
to prepare peptides in the pure state, manuscripts like this ‘compromising
with mixtures’ (p.3) cause me some anxiety." In his letter of May 15,
1990, Professor Hruby wrote that the paper may be acceptable only after major
revision. After doing further peptide separations using HPLC, the revised
version of the paper was accepted on November 21, 1990, and appeared in print
in June 1991 .
I have heard rumors that there were some disappointing events
connectedwith your publication. Could you tell us what these events were?
Our paper appeared 16 months after submitting the manuscript.
During thisperiod, patent applications were submitted by four different groups
all basedon our split-mix method: Huebner and Santi (Chiron group)  on
May 15,1990, Lam et al. (Salmon-Hruby group)  on July 2, 1990, Houghten
et al.(Richard Houghten's group)  on November 21, 1990 and DiMarchi et
al. (EliLilly group)  on June 18, 1991. It was particularly painful that
ProfessorHruby, the Editor-in-Chief of the journal where our manuscript was
submitted,participated in patenting and his group also submitted a paper
to Nature and presented a lecture to the 12th American Peptide Symposium
,claiming in both papers that they invented the split-mix method. Shortly
after the appearance of our paper, Dr. Richard Houghten and his group (Torrey
Pines Institute for Molecular Studies, San Diego) made also a presentation
at the Symposium on the Innovation & Perspectives in Solid Phase Synthesis
and Related Technologies  and submitted a paper to Nature  in which
our split-mix synthesis was described. I would also like to call your attention
to a remarkable coincidence. The number of the filed patents was exactlythe
same as the number of those that had had access to our manuscript: theeditor
of the journal and three reviewers. Do you think that such a radicallynew
idea like that of the split-mix synthesis may suddenly and independentlyoccur
in four different heads not earlier and not later but exactly at thesame
time when our manuscript is being reviewed for publication, andone
of those heads is that of the chief editor of the journal (or of oneof his
associates) to which our manuscript had been submitted?
Possible, but unlikely. Let me ask you this: Did you
have personalcontacts with Professor Hruby at this time?
I did. Our contacts began in the following way. In January
1991, Igot a letter from Dr. Kaubisch, Vice President of Selectide Corp.
and heoffered to visit us to discuss the possibilities of cooperation. He
explainedthat Selectide was founded at the end of 1990 (well after our paper
had beensubmitted) by Professor Hruby and others at the University of Arizona.
Dr. Kaubisch also mentioned in the letter that they saw the abstract of our
presentation to the 10th International Symposium of Medicinal Chemistry (Budapest,
1988). Dr. Kaubisch came to Budapest in February 1991 and heexplained
that one of them found out that in the split-mix synthesis onepeptide forms
on each bead and they developed a screening method based onthat. He invited
me to visit Selectide to give a seminar and discuss thepossibilities of cooperation.
I accepted the invitation and my visit tookplace in early April 1991.
I gave a seminar on April 2 at the CancerCenter of University of Arizona,
Tucson, speaking about the split synthesisand the stepwise screening strategy
I described in the 1982 document. Dr.Lam (first author), Professors Hruby
and Salmon (director of the ArizonaCancer Center and Dr. Lam’s boss)
as well as other authors of theirlater papers and the earlier patent application
were among the audience.After they asked me to sign a confidentiality document,
with which I complied,they offered me a consultancy (which was never realized),
and showed me theirscreening method. As a possibility of cooperation, however,
they suggestedto me to do analytical experiments with non-natural amino acids
they usedin peptide synthesis. I found this offer inappropriate and told
them thatour cooperation should be connected with our synthetic method. Finally
weagreed to continue the discussions by mail but the cooperation was never
realized because of later events.
When did you sense for the first time that something went wrong?
A few months after my visit to Tucson, one of my former students
attendedthe 12th American Peptide Symposium in Boston in June 1991. She told
me thatDr. Lam had an oral presentation reporting about the split-mix synthesis
and their screening method  but made no reference to our work. Lateron,
one of my colleagues took part in the Symposium on the Innovation &Perspectives
in Solid Phase Synthesis and Related Technologies in August1991, where Richard
Houghten presented our synthetic method as his own .Yet later, I found
in Nature the papers of Lam et al.  and Houghten etal.  that appeared
in September 1991 and in which they described thesplit-mix synthesis as their
own invention and without any reference to ourpapers.
How did you feel about this and what could you do in this situation?
I have to tell you that this situation has caused me much bitterness
throughthe years. As my first reaction, I wrote a letter to both parties
askingfor a correction in Nature and citation of our papers.
What was their reaction?
Let me speak first about the Hruby group. Both Professor Hruby
and Dr. Lamwrote me an apologizing letter stating that in the first version
of theirNature papers, there was a reference to our work but they had to
shortenthe manuscript and the reference was deleted. They also promised to
publisha correction in Nature. First of all I have to note that if you read
thepaper, you don't get the impression that anything was left out. They described
the synthetic method as their own invention and in later papers they called
it the Selectide process. After almost one year of delay, their correction,
with an ambiguous content, appeared in Nature . My name, however, was
misprinted: Fukura instead of Furka. After repeated correspondence, a correction
of the correction appeared in Nature in December 1992 .
I questioned the explanation of omitting the references to our
papers byHruby and Lam from the beginning. Later on, I found evidence that
convincedme that omitting us from the list of references vas intentional.
They havepublished other papers and documents from which citation of our
work is alsomissing. Let me mention only two examples.
(i) Around the time of publishing the Nature paper Professor Hruby
and someof his co-workers wrote a chapter in a book  in which the split-mix
synthesisis also mentioned without reference to our contribution.
(ii) Professor Sydney E. Salmon of the University of Arizona (one
of theauthors of the Nature paper ) had grant applications in cooperation
withHruby and others based on the split-mix synthesis. The synthesis was
indicatedin their proposals as their own invention. One of the successful
proposalsto the National Institutes of Health had the title "Discovery of
PeptideAnticancer Drugs," grant No. CA57723. This grant lasted from 1992
to 1995and brought more than 3 million dollars to the applicants. A copy
of thegrant application was in my hands and saw no reference in it to our
Let's turn now to Dr. Houghten. I also asked him to correct his
Nature paper. He promised to do that, called me by phone, and also offered
cooperationand financial support. He sent me the copy of the correction letter
supposedlymailed by him to Nature. He wrote in the letter "As we were unaware
of anyof Dr. Furka's work we did not include it as a reference in our manuscript.
We regret this omission ...". The correction, however, was never published.
It deserves to look closer what Dr. Houghten states in his letter: "we were
unaware of any of Dr. Furka's work." I later found Dr. Houghten's patent
application  in which he cited the abstract of our 1988 presentation in
Prague . The patent was filed on November 21, 1990, and the Nature paper
was submitted on July 31, 1991. Let me ask you: Could anybody believe that
what he knew in November 1990 was unknown to him eight months later?
Did you try to make other actions in addition to those outlined
Yes, but all of them were unsuccessful. I tried to publish myself
a letterin Nature, but this was declined by Professor Maddox, who was the
Editorat that time. I also contacted the Office of Research Integrity
ofthe Department of Health & Human Services of the U.S. I had long
correspondence with Dr. Alan Price of that office and sent him all the evidences.
Finally, he concluded that in his opinion no plagiarism occurred and advised
me to turn to the University of Arizona. I also contacted the Publisher of
the International Journal of Peptide and Protein Research, again withoutany
What was the effect of Drs. Hruby's and Houghten's actions
In addition to the bitterness that lasted for years, for a long
time onlytheir papers were cited in the literature. Later on, and still nowadays,
their work is often cited as independent from that of ours. I had difficulties
for years in publishing papers and had no possibility to give oral presentations
at peptide symposia. Many years later, a friend of mine who was chairmanof
a combinatorial session of a peptide symposium told me that he was instructed
by the organizers not to give me possibility for questions or comments.
Despite all this, the situation has gradually changed. I remember
that shortlyafter the appearance of Lam's and Houghten's Nature papers, I
got a letterfrom Professor W. C. Still of Columbia University, asking me
to clarify thepriority question by sending him earlier publications. I sent
him copiesthe two 1988 abstracts [3, 4] and the 1982 document [1, 2]. I also
made availablecopies of the 1982 document as a supplement to my posters presented
at symposia.As a consequence, people have realized that the real birthplace
of combinatorialchemistry was our laboratory in Budapest, and have begun
to be called the“pioneer” or the “father of combinatorial
chemistry.” I was elected Honorary President of the European
Society of CombinatorialSciences when this organization held its first symposium
in Budapest in 2001.
Some years ago, I already made an interview with you  and
you alsopublished a paper about the history of combinatorial chemistry ,
butyou did not speak about these problems. Why?
As mentioned before, my earlier efforts to clarify the priority
problemswere unsuccessful. What happened was a scandal in science and most
people,including myself, do not like scandals. Also, it is not easy
to speakabout such events in science, particularly if you are the victim.
My friendsalso advised me to be silent since those who speak out about such
things,the whistle blowers, are often considered as bad guys. Lately, however,
colleagues,whose opinion I respect, told me that it's time to bring out the
 FURKA, Á., Combinatorial chemistry: 20 years on....,
Drug Discovery today 7 (2002), pp. 1-7.
 FURKA, Á. – SEBESTYÉN, F. – ASGEDOM,
M. – DIBÓ, G., Cornucopia of peptides by synthesis, Abstr. 14th
Int. Congr. Biochem., Prague, Czechoslovakia, 1988, Vol. 5., p. 47.
 FURKA, Á. – SEBESTYÉN, F. – ASGEDOM,
M. – DIBÓ, G., More peptides by less labour, Abstr. 10th Int.
Symp. Med. Chem., Budapest, Hungary, 1988, p. 288.
 FURKA, A. – SEBESTYEN, F. – GULYAS, J., Computer
made electrophoretic peptide maps, Program of the 2nd International Conference
on Biochemical Separations, Keszthely, Hungary, Full Papers & Abstracts,
Edited by J. Pick, J. Vajda, pp. 35-42 (1988).
 FURKA, Á. – SEBESTYÉN, F. – ASGEDOM,
M. – DIBÓ, G., General method for rapid synthesis of multicomponent
peptide mixtures, Int. J. Peptide Protein Res. 37 (1991), pp. 487-493.
 HUEBNER, VERENA D. – SANTI, DANIEL V., Controlledsynthesis
of peptide mixtures using mixed resins. US Patent 5,182,366 (FiledMay 15,
 HOUGHTEN, R. A. – CUERVO, J. H., – PINILLA,C.
– APPEL Jr., J. R. – BLONDELLE, S., Synthesis of equimolecular
multiple oligomer mixtures, especially of oligopeptide mixtures, PCT patent
application, WO 92/09300 ( Filed November 21, 1990).
 LAM, K. S. –SALMON, S. E. – HRUBY, V. J. –
HERSH, E. M. – AL-OBEIDI, F., Random bio-oligomer library, a method
of synthesis thereof, and a method of use thereof, PCT patent application,
WO 92/00091 (Filed July 2, 1990).
 DIMARCHI, R. D. – GESELLSCHEN, P. D. – OWENS,
R. A.: Rapid synthesis and screening of peptide mimetics. Patent application,
filed June 18, 1991.
 LAM, K. S. – SALMON, S. E. – HERSH, E.
M. - HRUBY, V. J. – KAZMIERSKI, W. M. –KNAPP, R. J., A new type
of synthetic peptide library for identifying ligand-binding activity, Nature
82 (1991) p. 354.
 LAM, K. S. – SALMON, S. E., HERSH, E. M. –AL-OBEIDI,
F. – HRUBY, V. J., Rapid selection and structure determinationof acceptor
binding ligands from a large synthetic peptide library, Abstr.12th American
Peptide Symposium, Boston, USA, LW3.
 HOUGHTEN, R. A., New approaches for peptide and peptide-mimetic
biomedical drug discovery, Innovation & Perspectives in Solid Phase Synthesis
& Related Technologies, Second International Symposium, Canterbury, August
27-31, 1991, 10c.1.
 HOUGHTEN, R. A., PINILLA, C. – BLONDELLE, S.
– APPEL, J. R. – CUERVO, J. H., Generation and use of synthetic
peptide combinatorial libraries for basic research and drug discovery, Nature
84 (1991) p.354.
 Nature 258, 434 (1992).
 Nature 360, 768 (1992).
 HRUBY, V. J. – SHARMA, S. D. – COLLINS, N.–
MATSUNAGA, T. O. – RUSSEL, K. C., Application of SyntheticPeptides,
In: Synthetic Peptides. A User's Guide, G. A. Grant (Editor), W.H.Freeman
and Company, New York, 1992, pp. 270-272.
 I. Hargittai, The Chemical Intelligencer 6(2), 37-40 (2000);
I. Hargittai, Candid Science III: Conversations with Famous Chemists. Imperial
College Press, London, 2003, pp. 220-229.
 Á. Furka, History of Combinatorial Chemistry, Drug
Development Research 36, 1-12 (1995).