2,2,2-Trichloro-N-({2-[2-(dimethylamino)ethyl]-1,3-dioxo-2, 3-dihydro-1H-benzo[de]isoquinolin-5-yl}carbamoyl)acetamide (UNBS3157), a novel nonhematotoxic naphthalimide derivative with potent antitumor activity

Article abstract of DOI:10.1021/jm070315q

Amonafide (1), a naphthalimide which binds to DNA by intercalation and poisons topoisomerase IIα, has demonstrated activity in phase II breast cancer trials, but has failed thus far to enter clinical phase III because of dose-limiting bone marrow toxicity. Compound 17 (one of 41 new compounds synthesized) is a novel anticancer naphthalimide with a distinct mechanism of action, notably inducing autophagy and senescence in cancer cells. Compound 17 (2,2,2-trichloro-N-({2-[2-(dimethylamino)ethyl]-1,3-dioxo-2,3-dihydro-1H- benzo[de]isoquinolin-5-yl}carbamoyl)acetamide (UNBS3157)) was found to have a 3-4-fold higher maximum tolerated dose compared to amonafide and not to provoke hematotoxicity in mice at doses that display significant antitumor effects. Furthermore, 17 has shown itself to be superior to amonafide in vivo in models of (i) L1210 murine leukemia, (ii) MXT-HI murine mammary adenocarcinoma, and (iii) orthotopic models of human A549 NSCLC and BxPC3 pancreatic cancer. Compound 17, therefore, merits further investigation as a potential anticancer agent.

Full text of DOI:10.1021/jm070315q

4122
J. Med. Chem. 2007, 50, 4122-4134
2,2,2-Trichloro-N-({2-[2-(dimethylamino)ethyl]-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-
5-yl}carbamoyl)acetamide (UNBS3157), a Novel Nonhematotoxic Naphthalimide Derivative with
Potent Antitumor Activity
Eric Van Quaquebeke,† Tine Mahieu,† Patrick Dumont,†,| Janique Dewelle,† Fabrice Ribaucour,† Gentiane Simon,†
Se´bastien Sauvage,† Jean-Franc¸ois Gaussin,† Je´roˆme Tuti,† Mohamed El Yazidi,† Frank Van Vynckt,† Tatjana Mijatovic,†
Florence Lefranc,‡,§, Francis Darro,† and Robert Kiss*,‡,
Unibioscreen SA, 40 AVenue Joseph Wybran, 1070 Brussels, Belgium, Laboratoire de Toxicologie, Institut de Pharmacie, UniVersite´ Libre de
Bruxelles, Brussels, Belgium, and SerVice de Neurochirurgie, Cliniques UniVersitaires de Bruxelles, Hoˆpital Erasme, UniVersite´ Libre de
Bruxelles, Brussels, Belgium
ReceiVed March 19, 2007
Amonafide (1), a naphthalimide which binds to DNA by intercalation and poisons topoisomerase IIR, has
demonstrated activity in phase II breast cancer trials, but has failed thus far to enter clinical phase III because
of dose-limiting bone marrow toxicity. Compound 17 (one of 41 new compounds synthesized) is a novel
anticancer naphthalimide with a distinct mechanism of action, notably inducing autophagy and senescence
in cancer cells. Compound 17 (2,2,2-trichloro-N-({2-[2-(dimethylamino)ethyl]-1,3-dioxo-2,3-dihydro-1H-
benzo[de]isoquinolin-5-yl}carbamoyl)acetamide (UNBS3157)) was found to have a 3-4-fold higher
maximum tolerated dose compared to amonafide and not to provoke hematotoxicity in mice at doses that
display significant antitumor effects. Furthermore, 17 has shown itself to be superior to amonafide in vivo
in models of (i) L1210 murine leukemia, (ii) MXT-HI murine mammary adenocarcinoma, and (iii) orthotopic
models of human A549 NSCLC and BxPC3 pancreatic cancer. Compound 17, therefore, merits further
investigation as a potential anticancer agent.
Introduction
CYP1A2, but displays in vitro cytotoxicity similar to that of
amonafide.22 The variability in the clinical toxicity of amonafide
has been attributed to differential in vivo metabolism by NAT2.
The enzyme is highly polymorphic and individuals can be
classified, according to their metabolic activity, as slow or fast
acetylators.23 For most NAT2 substrates, toxic side effects are
associated with the slow acetylator phenotype. Amonafide is
an exception because it exhibits a significantly higher toxicity
in fast acetylators than in slow acetylators.24,25 Fast acetylator
phenotypes lead to increased metabolism to N-acetyl amonafide,
reduced oxidation of amonafide, and consequently, higher
exposure to more toxic compounds for longer periods than is
evident in slow acetylators.23-25
To minimize this toxicity, Chemgenex Pharmaceuticals
(Grovedale, Victoria, Australia) and Xanthus (Cambridge,
Massachusetts), who reinitiated the clinical development of
amonafide, were obliged to first phenotype patients using
caffeine as the NAT2 probe substrate to define slow and fast
acetylators and then adjust amonafide clinical doses, accord-
ingly. However, we have focused our efforts on synthesizing
derivatives of naphthalimide, with improved antitumor activity
and a significantly higher safety profile than amonafide. In
addition to amonafide (1), N-acetyl-amonafide (2), and amona-
fide’s nitro analog (3), 41 new naphthalimide derivatives (among
which 39 have been described by our group in WO2005/105753
patent)26 have been synthesized and evaluated because of their
novelty in cancer models in vitro and in vivo.
Isoquinolindione (naphthalimide) derivatives continue to be
of interest because in addition to being DNA intercalators they
have found application as fluorescent dyes and have some
potential in the synthesis of polymers.1-3 In therapeutics,
naphthalimides have been evaluated for photodynamic therapy4
and numerous derivatives have been evaluated as antitumor
agents,5-9 with a number, for example DMP840 (a bis-
naphthalimide derivative) and amonafide (NSC-308847, nafi-
dimide), a 5-amino-naphthalimide derivative, having reached
clinical trials.10,11 However, most have been abandoned because
of a poor therapeutic index. Amonafide (1), which acts as a
topoisomerase II poison,11-14 has completed several phase I and
phase II clinical trials. The compound has, however, with the
exception of advanced breast cancer,15,16 shown no activity or
only limited activity against a range of different cancer types.
Dose-limiting myelosuppression is also a key issue for the
compound.17-21 The compound’s toxicity, which is highly
variable, is linked to its metabolism. Amonafide can be
metabolized by N-oxidation (via CYP1A2) to generate a rapidly
eliminated inactive metabolite. Alternatively, it can be metabo-
lized by the enzyme N-acetyltransferase 2 (NAT2) to N-acetyl-
amonafide (2), a metabolite that is no longer a substrate for
* To whom correspondence should be addressed. Laboratoire de Toxi-
cologie, Institut de Pharmacie, Universite´ Libre de Bruxelles, Campus de
la Plaine, CP205/1, Boulevard du Triomphe, 1050 Brussels, Belgium.
Phone: +32 477 62 20 83. Fax: +32 23 32 53 35. E-mail: rkiss@ulb.ac.be.
† Unibioscreen SA.
Chemistry
‡ Institut de Pharmacie, Universite´ Libre de Bruxelles.
§ Hoˆpital Erasme, Universite´ Libre de Bruxelles.
The synthesis of amonafide (1) was carried out according to
a two-step process given in Figure 1.
The starting reactant used was the commercially available
3-nitro-1,8-naphthalic anhydride. The first step reaction pro-
ceeded with a 93% yield to furnish after filtration a yellow-
| Current Address: Service d’Anatomie Pathologique, Cliniques Uni-
versitaires de Bruxelles, Hoˆpital Erasme, Universite´ Libre de Bruxelles,
Brussels, Belgium.
R.K. is a Director of Research at the Belgian National Fund for
Scientific Research (FNRS, Belgium). F.L. is a Clinical Research Fellow
with the FNRS.
10.1021/jm070315q CCC: $37.00 © 2007 American Chemical Society
Published on Web 07/21/2007

NoVel Nonhematotoxic Naphthalimide DeriVatiVe
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 17 4123
Figure 1. The two-step reaction to obtain the synthon amonafide (1) from commercially available 3-nitro-1,8-naphthalic anhydride.
Figure 2. Schematic chemical modification to obtain new derivatives from amonafide (1) used as a synthon.
orange solid (3), with an HPLC-UV purity of 100% (a/a). The
reduction of the nitro function to an amino (reaction 2)
proceeded with a reasonable yield by Pd on carbon using
triethylamine and formic acid in refluxing ethanol. After
removing the catalyst by filtration, the addition of heptane was
used to precipitate (1) as a yellow solid, which was produced
with a 91% yield. The purity of the amonafide (1) was
determined by HPLC-UV to be 100% (a/a). The global yield
of the two steps was 84.6%. Detailed descriptions of these
chemical steps are included in the Supporting Information (SI).
Our chemical strategy then focused on modifications to the
aryl amino function of amonafide to render it less susceptible
to interaction with NAT2, with the aim of reducing the potential
toxicity of new analogues. A total of 44, additional naphthal-
imide derivatives were synthesized that can be divided into five
distinct subclasses (Figure 2): (i) amides (obtained by reacting
amonafide with different acyl chlorides), (ii) ureas (reacting
amonafide with isocyanates), (iii) thioureas (reacting amonafide
with isothiocyanates), (iv) imines (reacting amonafide with
aldehydes), and (v) amines (by reduction of the imines previ-
ously obtained in iv).
Table 1). In the same manner, some apparently inactive or
weakly active compounds in vitro displayed marked in vivo
antitumor activity (2, 27, 29, 33; Table 1). Collectively, these
data suggested that in vitro testing of naphthalimide derivatives
was not necessarily appropriate for identifying compounds with
potent in vivo activity and low hematotoxicity.
Among the more active in vivo antitumor compounds
(Table 1), that is, those associated with %T/C index values of
g200%, some displayed higher toxicity: MTDs of e40 mg/kg
(e.g.: 2, 9) compared to others, for example: 17, 19, 21, 27,
29, 33, and 35, which had MTDs of g80 mg/kg. Table 1 also
reveals that amonafide (1) was associated with weak in vivo
activity in the L1210 leukemia model (T/C ) 140%), while its
toxic metabolite, N-acetyl-amonafide (2), displayed high activity.
Of the 44 total naphthalimide derivatives evaluated in the course
of the present study, four (17, 27, 29, 33) were associated with
marked in vivo activity (T/C values >300% or close to 300%)
in the L1210 mouse leukemia model, with low in vivo toxicity
(MTDs g80 mg/kg).
Accordingly, it was decided to more rigorously investigate
the in vivo antitumor activity profiles of these four compounds
in comparison to amonafide (1) and N-acetyl-amonafide (2) in
the L1210 mouse leukemia model. Table 2 indicates that
amonafide in the dose range 2.5 to 20 mg/kg i.p. was associated
with weak in vivo antitumor activity, with %T/C values ranging
between 109 and 143% when administered four times a week
for two consecutive weeks on days 1-4 and 8-11 post-L1210
cell injection to mice on day 0. Higher doses of 1 were toxic.
Under an identical regimen, the N-acetyl derivative of amonafide
(2) displayed marked in vivo antitumor activity, but with a very
narrow therapeutic window (Table 2). Of the four novel
naphthalimide derivatives, 17, 27, 29, and 33, investigated, 17
demonstrated consistently high %T/C values 200-300% over
the dose range 10-160 mg/kg i.p. and the highest therapeutic
window (Table 2). These data prompted investigation whether
the higher therapeutic window of certain of these naphthalimide
The common synthon of all new derivatives generated in the
current work was amonafide (1).
Pharmacology
Characterization of the In Vitro Cytotoxic Activity, In
Vivo Maximum Tolerated Dose in Healthy Mice, and the
In Vivo Antitumor Activity (L1210 Mouse Leukemia Model)
of Synthesized Naphthalimide Derivatives. Table 1 reveals
that the most potent naphthalimide derivatives under study
displayed in vitro antiproliferative activity (IC50 values from
the MTT colorimetric assay) only in the µM range. Additionally,
no statistically significant (p > 0.05; Spearman rank correlation
test) relationships between in vitro IC50 values, in vivo MTD
values (tolerance) and in vivo antitumor activity in the L1210
mouse leukemia model (Table 1) were observed. This indicated
that the most potent compounds in vitro were not always
the most active in vivo (compounds 1, 4, 5, 11, 18, 22, etc;

4124 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 17
Van Quaquebeke et al.
Table 1. Compounds Synthesized, Their In Vitro Cytotoxic Activity, and Their In Vivo Activity and Tolerance

NoVel Nonhematotoxic Naphthalimide DeriVatiVe
Table 1. (Continued)
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 17 4125
a The in vitro antiproliferative activities of the 44 compounds are reported as IC50 values (in µM), determined using the MTT colorimetric assay on
culturing cancer cells in the presence of each drug for three days. These were determined in the six human cancer cell lines: Hs683 and U373-MG glioblastoma,
HCT-15 and LoVo colon cancers, MCF-7 breast cancer, and A549 non-small-cell lung cancer. b In vivo tolerance was determined as the maximum tolerated
dose (MTD in mg/kg), which represents the dose just below the lowest dose level that killed at least one mouse in a treatment group after a maximum of
28 days. c The mean IC50 value could not be determined, as one or more of the corresponding data points were higher than the threshold value.

4126 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 17
Van Quaquebeke et al.
Table 2. %T/C Survival Indices for L1210 Leukemia-Bearing Mice after Treatment with Selected Naphthalimidesa
dose level
cmpd 1
cmpd 2
cmpd 17
cmpd 27
cmpd 29
cmpd 33
(i.p.; mg/kg)
%T/C indices
%T/C indices
%T/C indices
%T/C indices
%T/C indices
%T/C indices
2.5
5
10
20
40
80
120
160
109
143*
122
121
49d
ntb
ntb
ntb
ntb
ntb
ntb
111
149*
300***c
48d
ntb
ntb
ntb
ntb
197**
205**
272***
300***c
281***
300***c
115
151*
148*
232**
300***c
42d
215
195
278
300***c
40d
150*
165*
295***
41d
47d
ntb
ntb
ntb
ntb
ntb
ntb
ntb
a *: p < 0.05; **: p < 0.01; ***: p < 0.001. The compounds were evaluated at specific dose levels in the range 2.5-160 mg/kg, dictated by their
individual MTD values (Table 1). Compounds were administered i.p. four times a week for two consecutive weeks (days 1-4 and 8-11), with treatment
starting the day following leukemia cell grafting into the mice (day 0). There were five mice per experimental group, and the potential therapeutic benefits
contributed by each compound are evaluated by means of the T/C index. When a compound is associated with a T/C index value equal to 300%, it is
considered to bring L1210 leukemia-bearing mice to the status of “long survivors”. b nt: not tested. c ls: long survivors. d t: toxic; p < 0.01.
Compound 17 Displays Similar or Higher In Vivo Anti-
tumor Activity than Amonafide (1). Of the multiple clinical
trials that have been carried out with amonafide (1) or that are
still ongoing, the most interesting data have been obtained in
breast cancer.15,16 For this reason, the antitumor activity of 17
(10 mg/kg i.v.) was first compared with that of 1 (10 mg/kg
i.v.; Figure 4A) and taxol (20 mg/kg i.v.; Figure 4B) in the
human MDA-MB-231 s.c. breast cancer model and then at a
dose of 160 mg/kg i.p. against 1 (20 mg/kg i.p.) in the syngeneic
s.c. mouse mammary MXT-HI cancer model (Figure 4C). The
MXT tumor originates from the mammary galactophorous ducts
and its MXT-HI variant is hormone-insensitive and highly
Figure 3. Determination of the potential hematotoxicity of compounds
metastasizing to the liver (the arrow in Figure 4D points to a
1, 2, 17, 27, 29, and 33. This was assessed in terms of platelet numbers,
large liver metastasis) when the primary tumor is grafted
in healthy mice receiving 15 i.p. administrations: three per week on
subcutaneously onto female B6D2F1 mice.27,28
Mondays, Wednesdays, and Fridays over five consecutive weeks. Each
compound was evaluated at two distinct dose levels. “n ) x” is the
number of mice from groups of 10 that survived the 15 administrations.
The data are presented as mean values ( SEM.
Figure 4A shows that 1 and 17 displayed similar in vivo
antitumor activity in their ability to decrease the growth
rates of human MDA-MB-231 breast cancer xenografts. The
MDA-MB-231 growing subcutaneously does not metastasize.
Figure 4B shows that the in vivo antitumor activity of 17 (and,
therefore, of 1) was similar to that of taxol in this human MDA-
MB-231 breast cancer xenograft model. These results for 17
must be considered with respect to the significant antitumor
activity observed for 1 and taxol in breast cancer patients.15,16
The experimental schedule used for taxol treatment in this
MDA-MB-231 breast cancer xenograft model was chosen on
the basis of optimized protocols published previously by Kraus-
Berthier et al.,29 with respect to the use of taxol in human
xenograft models.
derivatives: 17, 27, 29, and 33 offered a more favorable
hematotoxicity profile than 1 (amonafide) or 2 (N-acetyl-
amonafide).
Compound 17 Displays Weaker Hematotoxicity in Healthy
Mice than Amonafide and N-Acetyl-amonafide. Groups of
healthy mice (10 per group) received 1 (amonafide), 2, 17, 27,
29, or 33 three times a week (on Mondays, Wednesdays, and
Fridays) for five consecutive weeks. Each compound was
evaluated at two distinct doses, as detailed in Figure 3 and its
legend. The groups were sacrificed 3 days following the last
dose and blood samples were taken for determination of platelet,
red blood cell (RBC), and white blood cell (WBC) counts.
Figure 3 shows that the mice tolerated 15 chronic administrations
of 1 and 2 at 10 mg/kg, while all animals died before receiving
the complete set of 15 administrations of 1 at 20 mg/kg. Four
of the 10 mice receiving 20 mg/kg of 2 also died before the
end of the experiment, and the remaining six mice displayed a
marked decrease in their platelet numbers (Figure 3). The present
experiment, therefore, perfectly reproduced the known hema-
totoxicity of amonafide (1) and N-acetyl-amonafide (2).17-21
Compounds 27, 29, and 33 also displayed significant (p < 0.05
to p < 0.001) decreases in platelet numbers compared to controls
(Figure 3). In addition, 29 provoked severe decreases in RBC
counts (data not shown). The only naphthalimide derivative
studied that displayed no hematotoxicity (including not only
platelet but also RBC {data not shown} and WBC {data not
shown} counts) was 17 (Figure 3). Additional experiments have
been performed with chronic oral and i.v. treatment of 17. The
data are provided in SI as Table 3. At high doses, 17 decreases
the number of red blood cells and white blood cells, but not
the number of platelets (see Table 3 in SI).
Figure 4C shows that 1 and 17 displayed weak in vivo
antitumor activity in terms of their ability to reduce the growth
rates of mouse MXT-HI mammary tumors, which heavily
metastasizes to the liver (Figure 4D). In contrast, MXT-HI-
tumor-bearing mice treated with 17 survived significantly (p <
0.01) longer (T/C ) 183%) than those treated with 1 (T/C )
143%), a feature that may suggest higher antimetastatic effects
for 17 than for 1 in this mouse mammary tumor model. We are
currently investigating this hypothesis at the experimental
level.
Compound 17 Displays Similar or Higher In Vivo Anti-
tumor Activity than Irinotecan and Gemcitabine in Models
of Human NSCLC and Pancreatic Cancer, Respectively.
Figure 5A shows that 17 (10 mg/kg i.v.) significantly increased
the survival of A549 NSCLC orthotopic xenograft-bearing
mice, while 1 (amonafide) at the same dose level did not. The
activity of 17 in this A549 NSCLC orthotopic xenograft model
was of the same magnitude as that contributed by irinotecan
(Figure 5B). Figure 5Ca morphologically illustrates the almost
total destruction of the lung parenchyma by the A549 NSCLC

NoVel Nonhematotoxic Naphthalimide DeriVatiVe
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 17 4127
Figure 4. Compound-induced changes in tumor surface area (mm2) in s.c. models of human breast and mouse mammary cancers. (A) Immuno-
compromised mice implanted s.c. with human MDA-MB-231 breast cancer cells and treated i.v. with 1 (amonafide) or 17. (B) Immuno-compromised
mice implanted s.c. with human MDA-MB-231 breast cancer cells and treated i.v. with taxol or 17. (C) Immuno-competent mice implanted s.c.
with mouse MXT-HI mammary adenocarcinoma and treated i.p. with 1 or 17. For A-C, compounds 1 and 17 were administered using a schedule
of five successive injections per week for three weeks, with drug administration starting on day 14 post-tumor graft. Taxol was administered using
a schedule of one injection per week for three weeks, with drug administration starting on day 14 post-tumor graft. Each experimental group
contained nine animals. The data are presented as mean values ( SEM. The control group is the same in Figures 4A and 4B. (D) Morphological
illustration (HE staining; G × 200) of a large MXT-H1 mammary tumor metastasis (to which the black arrow points) developing in liver parenchyma
(LP).
orthotopic xenograft one month after grafting A549 cells into
the lungs. This A549 NSCLC orthotopic xenograft model gives
brain (Figure 5Cb) and liver (data not shown) metastases in
more than 80% of A549 NSCLC-bearing immuno-compromised
mice.30 Compound 17 (20 mg/kg i.v.) also showed similar
activity to gemcitabine (40 mg/kg i.v.; Figure 5D) in the
orthotopic BxPC3 pancreas cancer model (Figure 5Da), which
also gives prominent liver metastases (Figure 5Db).
our experimental conditions, amonafide (1) had a UC50 of
8 µM (Figure 6Aa) and that determined for 29 was similar at
13 µM (Figure 6Ab). In contrast, 17 had a higher UC50
(∼40 µM), which means a higher drug concentration is required
to induce the same topoisomer shift toward the supercoiled form.
Compounds 17 and 29 were then investigated to determine
whether they act as topoisomerase II poisons. Topoisomerase
II regulates DNA topology via a breakage-reunion cycle; an
activity necessary for the segregation of interlocked chromo-
somes at mitosis and the removal of excess supercoiling
generated during processes such as replication or transcription.36
After interacting noncovalently with DNA, topoisomerase II
simultaneously cuts both DNA strands and a covalent interme-
diate is then established between each subunit of the topoi-
somerase II homodimer and the newly created DNA 5′-
phosphate ends via phosphotyrosyl bonds.36 This transient
intermediate is called the cleavable complex because disruption
of the catalytic cycle at this stage results in a permanent protein-
associated DNA double-stranded break. Under normal condi-
tions, cleavable complexes are rapidly converted back to
noncleavable forms and, therefore, they exist at a very low
steady-state in cells.36 However, a number of antitumor drugs
are able to induce a drastic increase in the number of topoi-
somerase II-DNA covalent intermediates that are present in a
cell at a given time by inhibiting the religation step and by
enhancing the rate of cleavage. Ultimately, this situation results
in an accumulation of double-stranded DNA breaks and cell
death. Thus, topoisomerase II poisons convert the protein into
an intracellular toxin whose action damages the genome.36
An in vitro plasmid-based system was used to determine the
ability of test compounds to act as topoisomerase II poisons.
Compound 17 Is Not a Topoisomerase II Poison. Amona-
fide31 and amonafide derivatives32-35 intercalate with DNA and
poison topoisomerase IIR. The ability of 17 to act as a DNA
intercalator was, thus, first compared with that of 1 and 29
(which displays similar in vitro and in vivo antitumor effects
to 17 (Table 1), but has higher hematotoxic effects (Figure 3)).
DNA unwinding tests were performed using eukaryotic topoi-
somerase I (Figure 6A). The method is based on the ability of
topoisomerase I to negatively supercoil a relaxed plasmid in
the presence of a DNA intercalating agent. In a topoisomerase
I-containing reaction, the presence of a DNA unwinding/
intercalating agent will lead to the formation of a relaxed
“underwound” DNA molecule with a deficient linking number.
Upon removal of the intercalating agent, this relaxed “under-
wound” molecule converts to a supercoiled molecule, owing to
the recovery of the normal DNA twist. Figure 6A shows
representative results of such experiments in which the reactions
are performed in the presence of increasing concentrations of
the molecules to determine the UC50 of the test compounds.
The UC50 is the drug concentration at which the relaxed band
is shifted to the midpoint between the supercoiled and the
relaxed states. The results indicate that both 29 (Figure 6Ab)
and 17 (Figure 6Ac) are able to intercalate with DNA. Under

4128 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 17
Van Quaquebeke et al.
Figure 5. Compound activity in orthotopic models of human lung and pancreatic cancer. (A) The activity of i.v. administered 1 or 17 on the
survival of mice orthotopically grafted with human A549 NSCLC. (B) The activity of i.v. administered 17 or irinotecan on the survival of mice
orthotopically grafted with human A549 NSCLC. (Ca) Typical morphological illustration (HE staining; G × 100) of the development of a human
A549 NSCLC xenograft (A549xen) in the lung parenchyma (L) of an immuno-compromised mouse. This mouse was orthotopically grafted with
A549 tumor cells one month earlier. (Cb) Typical morphological illustration (HE staining; G × 100) of the development of human A549 NSCLC
xenograft metastases (see the black arrows) in the brain parenchyma (BP) of an immuno-compromised mouse one month after A549 cell grafting
into its lungs. (D) The activity of i.v. administered 17 and gemcitabine on the survival of mice orthotopically grafted with human BxPC3 pancreatic
cancer. (Da) Typical morphological illustration (HE staining; G × 200) of the development of a human BxPC3 xenograft (BxPC3xen) in the
normal pancreas (NP) of an immuno-compromised mouse. This mouse was orthotopically grafted with BxPC3 cells two months earlier. (Db)
Typical morphological illustration (HE staining; G × 100) of the development of a BxPC3 metastasis (see the black arrow) in the liver parenchyma
(LP) of an immuno-compromised mouse two months after BxPC3 cell grafting into its pancreas. Large areas of necrosis (NA) are induced by this
metastatic process (Figure 5Db). Plots A, B, and D display the survival of the mice (n ) 9) in each group expressed as the decreasing cumulative
proportion of those surviving (Kaplan-Meier survival analysis). The control group is the same in Figures 5A and 5B.
This assay measures the conversion of a covalently closed
supercoiled plasmid into linear molecules as a consequence of
stabilization of cleavable complexes leading to plasmid double-
strand breaks. As shown in Figure 6B, compounds were tested
at concentrations ranging from 6 to 100 µM. The results obtained
indicated that 29 (Figure 6Ba) is a topoisomerase II poison that
is at least as potent as amonafide (1; Figure 6Ba) and its
metabolite N-acetyl-amonafide (2; Figure 6Bb). For each of
these compounds, 50 µM was the concentration required for
an optimal stabilization of the cleavable complex. Compound
17 did not act as a topoisomerase II poison in this assay
(Figure 6Ba). Indeed, when compared to the control reaction
performed in the absence of test compounds, no increase in the
intensity of the linear band was observed after treatment with
17 (Figure 6Ba).
Various intercalating agents also have the ability to inhibit
the strand-passage activity of topoisomerase II, in turn prevent-
ing the enzyme’s ability to catalyze the double-strand cleavage
of DNA and the passage of a second DNA duplex through the
transiently established break. Accordingly, test compounds were
also evaluated in the classical kinetoplast DNA (kDNA)
decatenation assay.37 Kinetoplast DNA is found in the mito-
chondria of protozoa and consists mainly of a large network of
interlocked (catenated) mini-DNA circles of about 2.5 kb each.
Topoisomerase II is able to decatenate this network into free
mini-circles. Compounds 1, 17, and 29 were tested at 50 µM
for their ability to inhibit topoisomerase II-mediated kDNA
decatenation. Compounds 17 and 29 as well as amonafide (1)
inhibited this specific activity of topoisomerase II. Thus,
although 17 does not seem to act as a topoisomerase II poison

NoVel Nonhematotoxic Naphthalimide DeriVatiVe
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 17 4129
Figure 6. Ability of amonafide (1), N-acetyl amonafide (2), UNBS3157 (17), and 29 to act as DNA intercalating agents and to interfere with
topoisomerase II activity. (A) The new amonafide derivatives are DNA intercalating agents of various potencies. Intercalation was monitored by
conversion of relaxed pBR322 plasmid to supercoiled molecules, in the presence of topoisomerase I. Shown here are pictures of ethidium bromide
stained agarose gels displaying the results of unwinding experiments for each molecule tested. Molecules were included in the reactions at final
concentrations ranging from 4 to 32 µM, except for 17 (15-55 µM). The position of the supercoiled (Sc) and relaxed (R) pBR322 forms is
indicated on each gel. A: substrate (relaxed pBR322); B: supercoiled pBR322 (marker); C: control reaction performed in the absence of test
compounds, but with the addition of solvent alone (DMSO). (B) UNBS3157 (17) does not cause pBR322 linearization in the presence of topoisomerase
IIR. The stimulation of topoisomerase II-dependent DNA cleavage is observed by an increase in the intensity of the linear pBR322 band (L),
corresponding to an enhancement of cleavable complex stabilization. In these reactions, supercoiled pBR322 was relaxed in the presence of 10
units of topoisomerase IIR. Amonafide (Ba), its N-acetylated metabolite (Bb), as well as 17 (Ba) and 29 (Ba) were tested at various concentrations,
ranging from 6 to 100 µM. Etoposide (Eto, Ba), a well-known topo II poison, was used as a positive control at a concentration of 50 µM. L: linear
marker (pBR322 digested with Eco RI); Sc: supercoiled marker (no enzyme reaction); R: relaxed marker (control reaction in the presence of
solvent but without added test compounds). Arrows indicate the positions of the relaxed (R), the supercoiled (Sc), the linear (L), and the nicked
open circular (NOC) forms. (C) The inhibition of topoisomerase II strand-passage activity was measured by a kDNA decatenation assay. Catenated
kDNA remains localized in the wells due to the large size of the network, while decatenated kDNA is able to enter the gel. An agarose gel stained
with ethidium bromide is shown. The test compounds were evaluated in the reactions at a concentration of 50 µM (no enzyme: negative decatenation
control; and no drug: positive decatenation control).
(Figure 6B), it is, however, able to inhibit its strand-passage
activity (Figure 6C). Additional results indicate that none of
the tested molecules inhibit the strand-passage activity of
topoisomerase I even at high concentrations (data not shown).
Compound 17 Does Not Induce Apoptosis in Human PC-3
and DU-145 Prostate Cancer Cells, but Does Induce Au-
tophagy and Senescence. A hallmark of topoisomerase II-
targeting drugs is the induction of apoptosis. This is the

4130 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 17
Van Quaquebeke et al.
consequence of an intracellular increase in the level of DNA
damage provoked by stabilization of the cleavable complex and
a failure to achieve complete chromosome segregation as a result
of inhibition of topoisomerase II strand-passage activity.36
Amonafide and amonafide analogues, that is, R16, are topoi-
somerase II inhibitors that induce apoptosis.32 Flow cytometry
was used to determine the percentage of human PC-3 and DU-
145 prostate cancer cells that underwent apoptosis (i.e., positive
for both Annexin V and propidium iodide) when treated with
17. It was observed that only ∼10% of PC-3 (the gray bars)
and up to 15-20% DU-145 (the black bars) cells underwent
apoptotic processes following treatment with 17 at 10 µM
(Figure 7Aa).
therefore explain, at least partly, why both ADR and 17 failed
to induce marked senescence in PC-3 cells, while they both
did in DU-145 cells (Figure 7Db). Indeed, agents that induce
telomere shortening can also trigger a cell to enter senes-
cence.44,46 In this case, a senescence program is initiated that
induces the activation of various cell-cycle inhibitors and
requires the function of p53.44,46 It has been confirmed that
compound 17 does not shorten PC-3 telomeres (data not shown).
Discussion
Naphthalimides, a class of compounds that bind to DNA by
intercalation have shown high anticancer activity against a
variety of murine and human tumor cells.48 Two representatives,
mitonafide and amonafide, were evaluated in clinical trials as
potential anticancer agents.48 The therapeutic properties of these
initial lead drugs have been improved by designing bisinterca-
lating agents.49-51 One of these, elinafide, which has shown
marked in vitro and in vivo activity, has also been evaluated in
clinical trials against solid tumors.48,52
In the present study, it has been demonstrated that compound
17, obtained in three chemical steps from commercially available
3-nitro-1,8-naphthalic anhydride, is a novel anticancer naph-
thalimide26 with in vitro antiproliferative activity (IC50 range
of 0.8-1.8µM) against human cancer cell lines, including
glioblastoma (Hs683 and U373-MG), colorectal (HCT-15 and
LoVo), non-small-cell lung cancer (A549), and breast cancer
(MCF-7), similar to that of amonafide (1: IC50 range of 2.7-
5.8 µM), which has reached clinical phase II and demonstrated
activity notably in breast cancer.15,16 Amonafide (1) has failed
thus far to enter phase III because of dose-limiting bone marrow
toxicity, leading to thrombocytopenia, anemia, and leukopenia,
which is linked to its metabolism (via a polymorphic enzyme,
Compound 17 failed to induce activation of p53 in PC-3 cells,
which is a p53-deleted cell line (Figure 7Ab).38 DU-145 cells
express constitutively higher levels of p53 (Figure 7Ab), which
is typical of cells containing mutant p53 compared to human
MCF-7 breast cancer cells (Figure 7Ba) that express wild-type
p53.39,40 p53 was indeed constitutively activated in DU-145 cells
and 17 did not further activate p53 (Figure 7Ab). Adriamycin
(ADR) was chosen as a positive control for p53 activation in
MCF-7 breast cancer cells (Figure 7Ba). While both 1 and 29
markedly activated p53 in MCF-7 cells, 17 did not (Figure 7Bb).
The absence of clear 17-induced apoptosis in PC-3 and DU-
145 prostate cancer cells was further evidenced by the absence
of any procaspase-3 and -9 activation and also by the absence
of clear PARP cleavage in both PC-3 and DU-145 prostate
cancer cells treated with 17 (Figure 7Ab). Taken together, these
data appear to rule out a potential pro-apoptotic effect for 17.
However, pro-autophagic effects were observed in PC-3 and
to a markedly lesser extent in DU-145 cells treated with 17
(Figures 7Ca and 7Cb). This was initially assessed by the
quantification of acidic vesicular organelles, including autoph-
agic vacuoles in compound-treated cells using acridine orange
staining (Figure 7Ca). The percentage of cells with positive red
staining increased from approximately 5 to 35% in PC-3 cells
treated for 72 h with 10 µM of 17 (gray bars in Figure 7Ca).
The maximum of autophagic DU-145 cells did not exceed 10%
with the same treatment (Figure 7Ca). Second, cellular changes
in the expression of LC3 (a specific autophagy marker;
Figure 7Cb) on treatment with 17 were assessed.41,42 LC3 is
microtubule-associated protein 1 light chain 3, which is the
autophagosomal orthologue of yeast Atg8/Aup7.41-44 In un-
treated control cells, LC3 type I (LC3-I) and LC3 type II (LC3-
II) were expressed at higher levels in DU-145 than in PC-3 cells
(Figure 7Cb); a feature that could at least partly explain why
17 induced less pro-autophagic effects in DU-145 compared to
PC-3 cells (Figure 7Ca). Drug-induced pro-autophagic effects
are paralleled by a significant increase in the percentages of
cells in the G2 phase of the cell cycle.43 This feature was clearly
observed when PC-3 cells were treated for 72 h with 10 µM of
17 (the upper panel in Figure 7Da) but not when DU-145 cells
were treated in the same manner (the lower panel in Figure 7Da).
N-acetyltransferase 2) to
a toxic metabolite, N-acetyl-
amonafide.23-25 Compound 17 (2,2,2-trichloro-N-({2-[2-(dim-
ethylamino)ethyl]-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-
5-yl}carbamoyl)acetamide (UNBS3157)) has been designed to
avoid the metabolism that provokes the clinical hematotoxicity
of amonafide. Accordingly, in mice, compound 17 was found
to have a 3-4-fold higher maximum tolerated dose compared
to 1 irrespective of administration route and to provoke
significantly weaker hematotoxicity in mice than 1. Furthermore,
17 has shown itself to be superior to 1 in vivo in models of (i)
L1210 murine leukaemia, (ii) MXT-HI murine mammary
adenocarcinoma (note the improved %T/C values in the
Experimental Section), and (iii) orthotopic models of human
A549 NSCLC and BxPC3 pancreas cancer.
Preliminary data indicate that the mechanism of action of 17
is in part different to that of 1, which is described as a DNA
intercalating agent and topoisomerase II poison.11-14 Compound
17 demonstrates 5-fold weaker intercalating activity than 1, and
although able to inhibit topoisomerase II-mediated kinetoplast
DNA decatenation, it does not appear to be a topoisomerase II
poison, unlike 1. Furthermore, in breast carcinoma cells, 17 does
not induce rapid, marked, and sustained up-regulation of p53,
unlike 1, and it does not induce type I programmed cell death
(apoptosis) as the result of its antitumor activity. In contrast,
17 induces type II programmed cell death (autophagy) in human
p53-null prostate cancer cells (PC-3 cell line), but not in, or
only weakly so, human p53-mutated (but still functional)
prostate cancer cells (DU-145 cell line). In contrast, compound
17 induces senescence (cell proliferation arrest) in the p53-
mutated DU-145 prostate cancer cells, but does not do so, or
only induces this effect to a markedly lower extent, in p53-null
PC-3 cells. Compound 17 displays antiproliferative activity
Compound 17 seems to induce autophagy in PC-3 cells but
not in DU-145 cells, while the reverse feature has been observed
with respect to senescence. Using SA-â-galactosidase staining,
a specific marker for senescence,45,46 it was observed that DU-
145 cells treated for 72 h with 10 µM 17 underwent marked
processes of senescence, while PC-3 cells did so but to a
markedly lesser extent (Figure 7Db). A moderate concentration
(20 nM) of adriamycin (ADR) was used as the positive control
(Figure 7Db) to induce senescence in wild-type as well as p53-
mutated human cancer cells.47 As indicated above, PC-3 cells
are p53-null not p53-mutated (Figure 7Ab), a feature that could

NoVel Nonhematotoxic Naphthalimide DeriVatiVe
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 17 4131
Figure 7. UNBS3157 (17) does not induce apoptosis but has potent pro-autophagic effects or induces senescence in specified human prostate
cancer cells. (Aa) Drug-induced apoptotic effects as evaluated by flow cytometry with Annexin V-FITC staining of PC-3 (gray bars) or DU-145
(black bars) prostate cancer cells after treatment for 72 h with 0 (Ct: untreated cells), 1, or 10 µM UNBS3157 (compound 17). (Ab) Immunoblotting
determination of UNBS3157 (17)-induced effects on p53, PARP, procaspase-3, and procaspase-9 expression and activation in PC-3 and DU-145
cells. UNBS3157 effects were evaluated over 72 h at 1 and 10 µM in comparison to untreated (Ct) cells. (Ba) Adriamycin (ADR; 2.5 µM for 24
h) was chosen as a positive control for p53 activation in MCF-7 breast cancer cells. (Bb) Immunoblotting evaluation of 20 µM amonafide (which
is known to intercalate DNA and poison topoisomerase IIR) and UNBS3157 (compound 17) effects on p53 activation in MCF-7 human breast
cancer cells. Tubulin immunobloting was used as a loading control. (Ca) Drug-induced pro-autophagic effects as evaluated by quantification of
acidic vesicular organelles (revealed as red fluorescent staining), following acridine orange staining of PC-3 (gray bars) or DU-145 (black bars)
cells after treatment for 72 h with 0 (Ct, untreated cells), 1, or 10 µM UNBS3157 (17). (Cb) Cell lysates of PC-3 and DU-145 cells treated for 72
h with 1 and 10 µM UNBS3157 (17) were analyzed by Western blotting for LC3-I/II expression using an antibody kindly provided by Dr. Yasuko
Kondo (MD Anderson Cancer Center, Houston, TX). (Da) Drug-induced effects on the cell cycle as evaluated by propidium iodide (PI) staining
of PC-3 (upper panel) or DU-145 (lower panel) human prostate cancer cells after they had been treated for 72 h with 0 (Ct, untreated cells), 1, or
10 µM UNBS3157 (17). Cell cycle phases are divided into G2/M phase (black bars), S phase (gray bars), and G0/G1 phase (white bars). (Db)
Quantification of the induction of senescence-associated â-galactosidase activity in PC-3 and DU-145 cells following 10 µM UNBS3157 (17)
treatment for 72 h. Adriamycin (ADR; 20 nM) was used as the positive control in these experiments. The results are expressed as the percentage
of senescence-associated â-galactosidase positive staining.
against a wide range of different human cancer cells, but it
appears that the nature of its anticancer effects (i.e., autophagy
versus senescence) may be dependent on the status of p53 in
these cancer cells.
It must be remembered that cancer cells, in their relentless
drive to survive, hijack many normal processes including cell
cycle signaling, angiogenesis, glucose metabolism, apoptotic cell
death, and multidrug resistance mechanisms, all mechanisms

4132 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 17
Van Quaquebeke et al.
Statistical Analyses. A statistical comparison of the control and
treated groups was initially undertaken with the Kruskal-Wallis
test (a nonparametric one-way analysis of variance). Where this
revealed significant differences, the Dunn multiple comparison
procedure (two-sided test) was applied. However, this was adapted
to the special case of comparing treatment and control groups in
which only (k - 1) comparisons were undertaken among the k
groups tested by the Kruskal-Wallis test (instead of the possible
k(k - 1)/2 comparisons considered in the general procedure). The
levels of statistical significance associated with the %T/C survival
indices were determined by using Gehan’s generalized Wilcoxon
test. A correlation between the numerical variables was analyzed
by means of the nonparametric Spearman correlation test. All these
statistical analyses were carried out using Statistica (Statsoft, Tulsa,
Oklahoma).
in which p53 exerts more or less an important role. Induction
of autophagic cell death and senescence has clear clinical
potential in treating cancers with apoptotic defects.41-44,53
Glioblastomas and melanomas are typical examples of cancers
that are resistant to apoptosis.54,55 Temozolomide, a pro-
autophagic drug, shows promising therapeutic benefits in the
context of these two types of cancers.43,54-56 Other apoptosis-
resistant cancers, including NSCLCs and pancreatic cancers,
warrant intensive investigation with pro-autophagic drugs.30,57,58
In conclusion, the novel naphthalimide 17, which has a
distinct mechanism of action in comparison to amonafide, also
displays in vivo higher antitumor activity in a range of cancer
models and higher tolerance and significantly weaker hemato-
toxicity at “therapeutic” doses. Compound 17 therefore merits
further investigation as a potential anticancer agent.
Acknowledgment. The present work was financially sup-
ported by grants awarded by the “Re´gion de Bruxelles-Capitale”
(Brussels, Belgium).
Experimental Section
Chemistry. The chemical modifications to amonafide that have
been realized are summarized in Table 1 and are described in greater
detail in the SI.
Supporting Information Available: Methods, experimental
protocols, and 1H NMR, 13C NMR, ESIMS or EIMS, and IR
spectral data. This material is available free of charge via the
Internet at http://pubs.acs.org.
Pharmacology. In Vitro Pharmacology: Cell Lines. Human
cancer cell lines were obtained from the American Type Culture
Collection (ATCC, Manassas, U.S.A.), the European Collection of
Cell Culture (ECACC, Salisbury, U.K.), and the Deutsche Sam-
mlung von Mikroorganismen und Zellkulturen (DSMZ, Braunsch-
weig, Germany). The eight cell lines evaluated were the Hs683
(ATCC code HTB-138) and U373-MG (ECACC code 89081403)
glioblastomas, the HCT-15 (DSMZ code ACC357) and LoVo
(DSMZ code ACC350) colon cancer, the A549 (DSMZ code
ACC107) non-small-cell-lung cancer (NSCLC), the MCF-7 (DSMZ
code ACC115) breast cancer, and the PC-3 (ATCC code CRL1435)
and DU145 (ATCC code HTB81) prostate cancer models.
Evaluation of In Vitro Cell Proliferation by Means of the
MTT Colorimetric Assay. The overall growth level of the human
cancer cell lines was then determined by means of the colorimetric
MTT (3-[4,5-dimethylthiazol-2yl]-diphenyl tetrazolium bromide,
Sigma, Belgium) assay, as detailed previously.59-62
In Vivo Testing. Maximum Tolerated Dose. The acute
maximum tolerated dose (MTD) was determined following single
i.p. administration of increasing drug doses to groups of three
healthy B6D2F1 female mice. Seven dose levels of each drug (2.5,
5, 10, 20, 40, 80, and 160 mg/kg) were evaluated. The MTD was
defined as the dose just below the lowest dose level that killed at
least one mouse in a treatment group after a maximum of 28
days.28,61
Hematological Analyses in Healthy Mice. Healthy B6D2F1
female mice (10 per group) received each compound i.p. using a
schedule of three administrations per week for five consecutive
weeks at two specified dose levels relative to their MTD. For drug
administration, the compounds were solubilized in DMSO/saline
(5:95 v/v). The mice were sacrificed 3 days post-final drug
administration, blood was collected, and hematological profiling
was undertaken by determining platelet, red blood cell (RBC), and
white blood cell (WBC) counts using a Coulter Counter T-890
(Coulter Electronics, U.S.A.).
In Vivo Evaluation of Antitumor Activity. The details of each
treatment are provided in the Experimental Section and also form
part of the legends to the figures. The rest of the information is
provided in the SI. The potential survival gain obtained using
naphthalimide derivatives was evaluated by means of the %T/C
index for the L1210 leukemia model28,63 and by means of survival
curve analyses for human orthotopic xenografts.30,62,64 The %T/C
index is the ratio of the median survival time of the treated animal
group (T) and that of the control group (C). Toxic effects are
indicated by %T/C indices of <75%. The benefit of chemotherapy
is considered to be significant when associated with %T/C indices
>130% (see Statistical Analyses).
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JM070315Q