Authors:

Marinus W. Lobbezoo

Herbert M. Pinedo

Abstract

The EORTC New Drug Development Office (NDDO) was established in 1984 and remained active in the field of anticancer drug development for 15 years. Part 1 of our article describes how NDDO was set up under the EORTC umbrella as an infrastructure for drug development; this part describes NDDO’s main achievements during this period. This article provides overviews of new experimental anticancer agents which were investigated in various development phases, including pharmaceutical development, preclinical toxicology, bioassay development, preclinical pharmacokinetics, phase I dose escalation studies and disease-oriented phase II studies. We highlight two drugs of special interest that emerged from NDDO’s preclinical and clinical program and were submitted for regulatory approval after subsequent large scale clinical studies by others: decitabine and apaziquone. Decitabine ultimately received regulatory approval for use in hematological malignancies. NDDO and its partners also contributed to the early clinical evaluation of docetaxel, gemcitabine, topotecan, ecteinascidin 743 and S-1, all of which eventually obtained regulatory approval in various cancer indications.

Introduction

Over the 15 years of NDDO’s existence, hundreds of compounds acquired from various sources were screened in tumor cell lines and animal models at partner institutes. Compounds showing promising antitumor activity were selected for preclinical development and taken through formulation development, stability testing, bioassay development, and rodent-only toxicology, in several cases supplemented by bulk drug substance production, production of clinical supplies and preclinical pharmacokinetics. Drugs with successfully completed essential preclinical development entered clinical phase 1 studies and several of these proceeded to disease-oriented phase II studies. In addition to compounds emerging from NDDO’s drug screening program, experimental agents from pharma/biotech companies entered NDDO’s preclinical and early clinical development program.

Only drugs for which NDDO’s involvement in preclinical and clinical development is documented in the literature are included in this paper. The relevant literature references are cited in Tables 1-3. It cannot be excluded that additional unpublished (pre)clinical development activities have been undertaken with some of these drugs.

Preclinical development

NDDO’s drug acquisition and screening efforts have been described in detail in Part 1 of this article. Based on promising antitumor activity in preclinical screening tests decitabine, apaziquone, rhizoxin, aphidicolin glycinate, LL-D49194α1, DABIS maleate, and carzelesin emerged as candidates for preclinical development (Table 1).

Pharmaceutical development

Compounds listed in Table 1 underwent formulation development, mostly aimed at a freeze-dried product that could conveniently be reconstituted at a clinical trial site. After successful formulation development, stability of the product was usually tested under different conditions to advise shipment and storage conditions.

Table 1. New drugs undergoing preclinical development by EORTC-NDDO, 1984-1999

Preclinical pharmacokinetics and metabolism

Several NDDO drugs underwent pharmacokinetic evaluation in animals by PAMM Group members to generate the pharmacokinetic and metabolism information to support subsequent or ongoing early clinical studies. In most cases, bioanalytical assays were developed for these studies by partner institutes. Pharmacokinetic evaluations were also conducted in several phase I and II studies as shown in Tables 2 and 3.

Preclinical toxicology

The main aims of preclinical toxicology studies coordinated by NDDO were to define a safe starting dose for phase I clinical studies and to identify the potential target organs of a drug’s toxicity. Rodent-only studies were conducted according to the ‘General guidelines for the preclinical toxicology of new cytotoxic anticancer agents in Europe’ (Anonymous 1990).

Experimental agents evaluated in this way by NDDO are listed in Table 1. NDDO’s toxicology experience with selected drugs was summarized by Schwartsmann et al (1991a), Hendriks et al (1992a) and Henrar et al (1993).

Phase I and II clinical studies

Over the years, NDDO managed many phase I dose escalation studies (Table 2) and disease-oriented phase II studies (Table 3) of new anticancer agents. All studies were conducted in close collaboration with members of the EORTC Early Clinical Trials Group (ECTG) / EORTC Early Clinical Studies Group (ECSG). Overviews of some of the earlier drugs studied in the NDDO phase I and II program have been published by Schwartsmann et al. (1991b, 1991c).

Several drugs evaluated in phase I and/or II trials were offered for clinical testing in the NDDO-ECTG/ESG program by external parties, including pharmaceutical companies who wished to contract out (some of) their studies. Examples are gemcitabine, topotecan and docetaxel, which were ultimately approved and became frequently used anticancer agents in a range of indications.

Table 2. Drugs taken through phase 1 clinical studies by EORTC-NDDO and ECTG/ECSG, 1984-1999

Not all drugs with completed NDDO phase I studies were evaluated in phase II in the NDDO-ECTG/ECSG setting, partly because a recommended phase II dose (RP2D) and schedule could not be defined and partly because phase II studies were conducted by other clinical research organizations, for example with MEN-1075 and E7070. DABIS maleate did not proceed to phase II because by the end of the phase I studies it was discovered that the drug substance was potentially explosive. Aphidicolin glycinate also did not proceed to phase II evaluation, although a RP2D could be determined in phase I. The reason for this is currently unknown.

After the RP2D had been defined in phase I, non-randomized disease-oriented phase II trials were conducted, frequently with one drug being studied in multiple tumor types simultaneously. Tumor types were selected based on pre-existing knowledge about the drug under study, such as mechanism of action, structural analogy with clinically active anticancer agents, preclinical activity in HTX models or possible hints of clinical activity in phase I. An overview of published phase II studies conducted by NDDO-ECTG/ECSG is provided by Table 3.

Table 3. Disease-oriented phase 2 clinical studies by EORTC-NDDO and ECTG/ECSG, 1984-1999

Drugs of special interest

Two new drugs which successfully completed preclinical and early-phase clinical development illustrate the significance of the NDDO program: decitabine and apaziquone. Both were submitted for regulatory approval after positive large-scale clinical studies had been conducted following NDDO’s early-phase development efforts. Decitabine ultimately received FDA and EMA approval in hematological malignancies.

Decitabine

Decitabine (DAC; 5-aza-2'-deoxycytidine; NSC 127716) was one of the first drugs entering the NDDO development trajectory. This happened after Bob Pinedo had been picked it up at the NCI for further development in Europe. The drug was first synthesized by Pliml and Sorm in Czecho-Slovakia in the 1960s; Sorm and Vesely reported its antileukemic activity in vitro and in vivo in mice in 1968 (Sorm and Vesely, 1968). Momparler and colleagues in Canada characterized the drug as a hypomethylating with inhibition of DNA methylation as its mechanism of action.

The European development of decitabine by NDDO started in 1985 and included further preclinical antitumor testing, the development of an intravenous formulation and evaluation in the rodent-only toxicology program. The first phase I and pharmacokinetic study was conducted in patients with advanced solid tumors by dr. van Groeningen and colleagues from the Department of Medical Oncology, VUmc, Amsterdam (Van Groeningen et al, 1986). This study yielded valuable insights in the drug’s clinical toxicity profile, including dose-limiting myelosuppression, and its pharmacokinetic behavior in patients as well as the recommended dose for phase II studies using one-hour infusions. One partial response was noted in this study. Disease-oriented NDDO-ECTG phase II studies were subsequently conducted in five solid tumors (see Table 3) which yielded no indications of promising antitumor activity in these tumor types.

In parallel with the NDDO program, other groups in Europe and North America developed further intravenous dosing schedule and tested decitabine clinically in various hematological malignancies, sometimes with remarkable degrees of success. In 2006, decitabine received regulatory approval for acute myeloid leukemia in Europe (European Medicines Agency, Dacogen) and for myelodysplastic syndromes in the USA (Food and Drug Administration, DACOGEN®).

For an extensive review of the discovery, preclinical characterization and clinical development of decitabine up to 2005, see de Vos and van Overveld (2005).

Apaziquone

Apaziquone (originally named EO9) is a representative of a series of novel indoloquinones synthesized by dr. Eef Oostveen at the Department of Organic Chemistry, University of Amsterdam, under the supervision of Professor Nico Speckamp. The original idea behind this multi-institutional project, which was generously supported by grants from KWF Dutch Cancer Society, came from prof. David Reinhoudt, a chemist at Twente University, Enschede, The Netherlands. His idea was that bioreductively alkylating indoloquinones might serve as less toxic analogs of the established anticancer agent mitomycin-C. Oostveen synthesized a series of about 90 indoloquinones between 1982 and 1984 which were screened for antitumor activity in L1210 leukemia and rhabdomyosarcoma cell lines by Pinedo’s research laboratory at the VUmc. Between 1984 and 1988, the concept of bioreductive alkylation by these indoloquinones was further investigated in a range of preclinical models (Lobbezoo et al, 1989). Patent applications were filed in 1986-1987.

Apaziquone (3-hydroxymethyl-5-aziridinyl-1-methyl-2-(1H-indole-4,7-dione) prop-beta-en-alpha-ol), also known under the brand names EOquin, Neoquin and Qapzola, was selected as a candidate for development by the NDDO. In the preclinical phase, formulation development, plasma assay development, pharmacokinetic evaluation in animals, and rodent-only preclinical toxicology studies were performed (see Table 1). Phase I studies were performed in patients with solid tumors using 5-minutes weekly or 3-weekly iv infusions (see Table 2). These studies showed reversible proteinuria as the dose-limiting toxicity and yielded a maximum tolerated dose of 15 and 27 mg/m2, and a recommended dose for phase II studies of 12 and 22 mg/m2, respectively. Partial responses were noted in three patients (two in adenocarcinomas of unknown origin, one in bile duct cancer). However, subsequent phase II studies in five solid tumor types, listed in Table 3, failed to show signs of clinical antitumor activity. It was assumed that these failures were related to the very short half-life of the drug in human plasma and limited penetration in patients’ tumors. Therefore, in 1996 it was concluded that there was no future for apaziquone as a systemic anticancer agent. At that time, the licensing agreement with Kyowa Hakko, which had been closed in April 1992, was terminated. An overview of the early phase I and II studies with apaziquone has been published by Verweij et al (1994b).

Based on further basic and translational research, dr. Roger Phillips (University of Bradford, UK) in 2000 proposed that apaziquone might be useful as a local treatment for superficial bladder cancer. A new formulation for intravesical installation was developed and a small pilot study in patients with superficial bladder cancer, initiated by the University of Bradford, was remarkably successful. By that time, the involvement of NDDO in the development of apaziquone had been taken over by NDDO Oncology. The Bradford pilot study showed complete macroscopic and microscopic responses in 9/12 patients in the absence of systemic toxicity; only two patients experienced local toxicity of grade 2/3. These findings triggered a broader clinical trial program in bladder cancer, sponsored by Spectrum Pharmaceuticals under a new licensing agreement. A phase II study of apaziquone in patients with refractory superficial bladder cancer, undertaken by Prof. Alfred Witjes (Radboudumc, Nijmegen, The Netherlands) and colleagues from other Dutch hospitals, showed long-lasting complete responses in 67% of patients and limited local toxicity (Van der Heijden et al, 2006; Hendricksen et al, 2009). Based on these findings, Spectrum Pharmaceuticals sponsored two almost identical double-blind, placebo-controlled registrational phase 3 studies in low-risk, non-muscle invasive bladder cancer in 2007, each randomizing just over 800 patients. Apaziquone was instilled within 6 hours of transurethral resection and left in situ for one hour. Each individual study showed a statistically non-significant numerical improvement by apaziquone of the 2-year recurrence rate, the primary endpoint, compared to placebo. However, a combined post hoc analysis of both studies did show a statistically significant improvement of the 2-year recurrence rate (p=0.0096) (Karsh et al, 2018). An even better improvement was noted in the combined subgroups receiving apaziquone installation within 30-90 minutes of transurethral resection (21.8% difference in the 2-year recurrence rate; p=0.0009). Despite these positive data, the FDA rejected the new drug application submitted by Spectrum Pharmaceuticals on the basis of these studies (Broderick 2016). No further registrational studies have been undertaken and completed since, and the company ultimately decided to shelve the drug.

Reviews of the development of apaziquone as a potential treatment for superficial bladder cancer have been published by Phillips et al (2013), Phillips, Hendriks and Peters (2017) and Arends and Witjes (2018).

Brequinar sodium (DUP 785)

Although it was officially not an NDDO drug, brequinar sodium (DUP 785) deserves mentioning as it was the subject of the PhD thesis by NDDO Director Gilberto Schwartsmann while an NDDO employee (dr. Benjamin Winograd) was involved in its evaluation. The drug was studied extensively within the VUmc Department of Medical Oncology and was tested in phase I and translational studies (Schwartsmann et al, 1989, 1990; Peters et al 1990). Phase II studies in a range of tumor types by international groups of investigators, including the ECTG, unfortunately showed no or only limited clinical activity. Its development as an anticancer agent was discontinued. For a summary of the preclinical and clinical studies with brequinar sodium and its potential for the treatment of leukemia and inflammatory diseases, see Peters (2018).

Further drugs of interest

After the relationship between EORTC and NDDO had come to an end in 1998/1999 (see Part 1 of this article), several NDDO drugs under development at the time were handed over to NDDO Oncology, the successor to the EORTC New Drug Development Office. Among the drugs whose development was continued by NDDO Oncology as of 1999 were apaziquone, ecteinascidin 743 (ET-743; trabectedin), aplidine, MEN-1075, UFT, LU 103793 and E7070. ET-743 was also partly further developed within the EORTC, in particular for soft tissue sarcomas, and received EMA approval in this indication in 2007 (European Medicines Agency, Yondelis).

Another successful project undertaken in this new setting was the early clinical development of S-1 (tegafur/gimeracil/oteracil; Teysuno™). S-1 had been picked up by the VUmc Department of Medical Oncology in 1995 for further preclinical and clinical evaluation in Europe. Promising results of Japanese phase II studies with S-1 in gastric and colorectal cancer were presented at the 10th NCI-EORTC Symposium in June 1998 (Anonymous 1998b). VUmc clinical investigators, NDDO Oncology and ECSG members conducted a phase I study and pharmacokinetic studies of S-1 in patients with advanced solid tumors (van Groeningen et al, 2000; Peters et al, 2001; Peters et al, 2003). Phase II studies in gastric and colorectal cancer by ECSG members, in collaboration with NDDO Oncology, showed promising response rates and manageable toxicity (Chollet P, et al. 2003; van den Brande et al, 2003). Outcomes of further international clinical studies and European cohort studies formed the basis for EMA approval of S-1, as part of combination therapies, for advanced gastric cancer and metastatic colorectal cancer in 2011 (European Medicines Agency, Teysuno).

Conclusions

During its 15 years of operations, the EORTC New Drug Development Office (NDDO) has successfully managed an infrastructure for academic new drug development in oncology. Hundreds of compounds were tested for antitumor activity in the laboratory, several of which proceeded to pharmaceutical development, preclinical toxicology testing and clinical evaluation in phase I and II studies, conducted in close collaboration with the EORTC ECTG/ECSG. Once the value of this program had become known, also new drugs from pharmaceutical and biotech companies were offered for early clinical evaluation.

Several drugs evaluated in early clinical studies in this setting ultimately received regulatory approval in the EU and/or the USA after additional large-scale clinical evaluation by others had successfully been completed. Decitabine, gemcitabine, topotecan, docetaxel, S-1, and trabectedin received EMA and/or FDA approval for use in various cancer indications. Another agent (apaziquone) showed promising antitumor activity in superficial bladder cancer in phase III studies, but the ensuing new drug application was rejected by the FDA.

Disclaimer

Drugs referred to here as having been developed by NDDO or with NDDO’s involvement are those mentioned in publications. Therefore, this paper does not necessarily provide a full account of all drugs handled by NDDO between 1984 and 1999.

Acknowledgements

The authors gratefully acknowledge information provided for the development of this manuscript by dr. Eef Oostveen, prof. Jos Beijnen, dr. Denis Lacombe, prof. Jaap Verweij, dr. Cees van Groeningen, and prof. Frits Peters.

References

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