Phase I and Pharmacology Study of Camptothecin-20-O-Propionate Hydrate (CZ48) in Patients With Solid Tumors or Lymphoma
CZ48 is an analog of the topoisomerase I inhibitor Camptothecin (CPT). CPT is an alkaloid
extracted from the Chinese tree, Camptotheca acuminata. Only the S isomer (the natural
form) is biologically active. The intact E lactone ring, which tends to be preserved in an
acid environment, is essential for anti-tumor activity. Moreover, the open lactone ring
moiety tends to promote toxicity [1-3]. In phase I and II trials conducted from 1970-1972
with the sodium salt of CPT (later shown to be largely inactive) toxicities included
myelosuppression, diarrhea and cystitis [2, 3].
With the observation in 1984 that the mechanism of action of CPT was through topoisomerase I
inhibition , renewed interest in the drug led to the development of a variety of analogs,
some of which had higher potency than the parent drug. Some derivatives are water soluble
such as CamptosarÂ® (irinotecan, CPTÂ¬-11) and HycamptinÂ® (topotecan), which are currently
approved for use in the USA for colon and ovarian cancers, respectively. Studies have shown
that substitutions at the C-9 and C- 10 positions enhance activity, and may confer water
solubility. In general, analogs that are water-soluble have reduced anti-cancer activity in
The water-insoluble native camptothecin (CPT) caused diarrhea, which proved to be the dose
limiting toxicity. Measurements demonstrated very little closed lactone ring CPT in the
plasma of subjects receiving this compound . This was later explained by the
demonstration that CPT binds to human albumin, an action which promotes opening of the
lactone ring . Mouse albumin is much less efficient in this activity, hence explaining
the greater antitumor activity observed in mice models.
In contrast to CPT, CZ48 incubated in vitro with human plasma and studied in vivo maintains
a substantial closed lactone ring concentration in the plasma. It appears to act as a
pro-drug. The removal of the side chain by endogenous esterases liberates the active drug,
CPT. Malignant cells have a high esterase content and are rapidly transforming the pro-drug
into the active parent drug. Preclinical studies suggest retention of anti-cancer activity
and reduction in toxicity, probably because the pro-drug in the systemic circulation has no
or little activity. Therefore, delivery of higher concentrations of closed lactone ring CPT
analog inside the tumor cells should potentiate the anti-tumor activity. This study offers
an opportunity to evaluate this hypothesis.
- OVERVIEW OF NONCLINICAL TESTING STRATEGY
All nonclinical pharmacology, pharmacokinetic, and toxicology studies described herein were
conducted by or for The CHRISTUS Stehlin Foundation for Cancer Research. For studies
conducted in accordance with GLP regulations, the location of records for inspection is/will
be included in each study report. For nonGLP studies, study records are retained on file
The CHRISTUS Stehlin Foundation for Cancer Research 1315 St. Joseph Parkway, Suite #1818
Houston, TX 77002
Several experiments were conducted to examine the primary pharmacodynamics (i.e., efficacy
and potency) of CZ48 against various tumor lines both in vitro and in vivo. In light of the
intended Phase I patient population, the CZ48 safety pharmacology package was limited to in
vitro and in vivo cardiovascular assessments. No secondary pharmacodynamic or
pharmacodynamic drug interaction studies were conducted with CZ48.
Note: For all GLP studies the purity of the CZ48 as determined by HPLC validated methods is
98.9%. For these studies, the drug was formulated in a 0.5% medium density carboxymethyl
cellulose aqueous suspension (CMC). For all non-GLP studies the drug (98% purity) was
formulated as a suspension in cottonseed oil (except the non-GLP study performed by Covance
which also used the CMC formulation).
Studies characterizing the pharmacokinetics and toxicokinetics of CZ48 and its active
metabolite camptothecin after either single- or repeat-dose administration were conducted in
mice and dogs. The repeat-dose studies were toxicokinetic evaluations conducted as part of
the pivotal toxicology program using validated bioanalytical methods. No extensive
distribution studies were conducted with CZ48; however, drug distribution into tumor, liver
and kidney tissues of tumor-bearing mice was evaluated. Several in vitro and in vivo
metabolism studies were conducted to examine the metabolic conversion of CZ48 to its active
moiety, camptothecin. Excretion studies were limited to measurement of CZ48 in the feces of
nude mice following single-dose administration. Pharmacokinetic drug interaction studies
were not conducted with CZ48.
The CZ48 toxicology program consisted of exploratory (nonGLP) dose range-finding studies in
the mouse and dog and definitive (GLP) toxicity and toxicokinetic studies in both species.
Pivotal toxicology studies conducted with CZ48 employed the intended clinical route and
schedule of administration. Additionally, two studies (nonGLP) were conducted in mice to
assess the general tolerability of chronic high-dose CZ48 administration.
Allocation: Non-Randomized, Endpoint Classification: Pharmacokinetics Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Treatment
To describe the dose limiting toxicities, adverse event profile, and Phase II recommended dose of Camptothecin-20-O-Propionate hydrate (CZ48).
Monte Shaheen, M.D.
University of New Mexico Cancer Center
United States: Institutional Review Board
|University of New Mexico Cancer Center||Albuquerque, New Mexico 87131-5636|
|University of Texas Health Sciences Center||San Antonio, Texas|