- Email: [email protected]
BIOACTIVITY OF CYCLOPHOSPHAMIDE PREPARATIONS
1436 had fallen
to
change in
pH.
70% of its
previous value.
There
was no
significant
Ng et al found that tumours in animals showed a decrease in the areas of their PCr peaks as they developed, possibly because a large of tumour cells became anoxic or hypoxic. PCr is an energy compound which can donate a phosphoryl residue to ATP when the ATP/ADP ratio falls; the equilibria of these reactions are such that the ATP concentration is maintained until almost no PCr is present. Thus the PCr peak will be a sensitive index of tissue metabolic state. After successful treatment by chemotherapy the tumour PCr peaks increased again in size.4 In the light of these animal data the fall in the PCr integral relative to those of the other peaks suggests that doxorubicin therapy was unsuccessful (or only partly successful) and that the tumour was developing. This is in accord with the clinical picture: the tumour did not decrease in size and the patient’s condition worsened after the second NMR examination, causing a third examination to be cancelled. It is at present very difficult to study human tumours in situ by NMR since few occur in accessible positions on the limbs. This case represented a rare (and, so far, unique) opportunity to study the evolution of a tumour and its response to chemotherapy. As further clinical experience becomes available NMR will help not only in the management of patients but also in giving a sense of direction to the biochemical study and the rational treatment of experimentally induced tumours in animals. mass
storage
We thank the Cancer Research Campaign, Science and Engineering Research Council, Action Research for the Crippled Child, Muscular Dystrophy Group of Great Britain, Special Trustees of University College Hospital, and the Wellcome Trust for financial support.
Department of Biochemistry, St George’s Hospital Medical School, London SW 17 0RE
J. R. GRIFFITHS
Department of Medical Physics and Bio-engineering, School of Medicine, University College London
E. CADY
Department of Medicine, School of Medicine, University College London
R. H. T. EDWARDS
Department of Nuclear Medicine, The Royal Marsden Hospital, Sutton
V. R. MCCREADY
Department of Physiology, University College London
Royal Marsden Hospital, London
D. R. WILKIE E. WILTSHAW
BIOACTIVITY OF CYCLOPHOSPHAMIDE PREPARATIONS
SIR,-Dr Shaw and colleagues (March 26, p 709) suggested that the ’Endoxana’ brand of cyclophosphamide (WB Pharmaceuticals) was more active in man and laboratory animals than the generic cyclophosphamide preparation from Farmitalia Carlo Erba. On the basis of differences in the intensity of several fragment ions in the mass spectrum these workers suggested that the two preparations might differ in their content of the two enantiomers of
cyclophosphamide. We have measured the optical activity of several samples of these cyclophosphamide preparations and repeatedly confirmed that for both compounds the optical rotation, at different wavelengths, is I zero-ie, both cyclophosphamides are identical racemic mixtures. Mass spectroscopy by fast atom bombardment or field desorption ionisation techniques revealed no differences in the chemical composition of the two preparations. However, electron impact spectra revealed minor quantitative variations which were caused by thermal rearrangement reactions during evaporation which, in turn, were related to the different crystal sizes of the two two
cyclophosphamides. If the samples were dissolved in water and the solvent subsequently evaporated within the mass spectrometer mlet system, the spectra of the two cyclophosphamides became identical. In addition, thermogravimetric analysis of both drugs resulted in superimposable curves, suggesting not only equal water contents in the two preparations but also, once again, chemical identity, Together with the identities of the nuclear magnetic resonance spectra and of the gas/liquid chromatography data, reported by Shaw et al, our findings clearly indicate that the two drugs are chemically alike. Minor difference between the two-eg, in crystal structure, storage times, and dissolution procedures-would probably not show up in pharmacological and toxicological tests. Since the starting point of Shaw and colleagues’ investigation was a clinical observation suggesting higher bladder toxicity of endoxana we have done some rat bladder toxicity assays.2Unlike Shaw et al we found no differences between the two compounds, provided the doses were adjusted to anhydrous cyclophosphamide, The dose/toxicity relationship after a single administration was identical. Equally, daily doses of 50 mg/kg of either preparation produced the same quantitative changes in the rat bladder. In addition, the spleen weights in all treated animals were dosedependently reduced, regardless of the cyclophosphamide preparation used. Thus WB Pharmaceuticals and Farmitalia Carlo Erba cyclophosphamide are by current analytical standards identical chemical entities and consequently possess the same pharmacological and toxicological profiles. Since its introduction into clinical practice by Asta-Werke 25 years ago, ’Endoxan’ (UK trade mark endoxana) has been related to anhydrous cyclophosphamide so that, for example, a 1 g vial contains 1069 mg monohydrate, corresponding to 1 g anhydrous active material. In contrast, the Farmitalia Carlo Erba product is specified on the basis of the monohydrate-ie, a 1 g vial contains only 936 mg of the active ingredient. Thus, although both products are declared as "I g cyclophosphamide", one contains 6-4% less active substance than the other. This may be clinically insignificant in low dose ranges, but with high cyclophosphamide treatment schedules, such as those mentioned by Shaw et al, the patient will probably receive more than 1 g cyclophosphamide less per treatment course if treated with the Farmitalia Carlo Erba drug. Cyclophosphamide induced bladder toxicity in man has a steep dose/toxicity curve, and the higher incidence of haemorrhagic cystitis following endoxana treatment could be explained solely by the higher dose administered. Bladder toxicity, even after ultrahIgh .doses of cyclophosphamide, can be effectively controlled by the simultaneous administration of adequate mesna doses;3however, differences in the therapeutic efficacy of the two cyclophosphamides are likely to occur and would definitively require dose adjustments. The extensive clinical experience with cyclophosphamide of the past three decades was exclusively based on endoxana, and all dose recommendations which have emerged from worldwide clinical research activities refer to the active (anhydrous) drug. Since all cytotoxic drugs have comparatively low therapeutic indices, the dose-specifications have to be exact and clear; generics should be matched with the original drug to avoid confusing doctors. pharmacists, and nurses and to maintain the comparability of clinical data. Asta-Werke AG, Degussa Pharma Gruppe, D-4800 Bielefeld 14, West Germany
U. NIEMEYER
Department of Physical Chemistry, Degussa Wolfgang, Hanau, West Germany
E. BUSKER
WB Pharmaceuticals Ltd, Bracknell, Berkshire
J. DALTON
2. Brock
Ng TC, Evanochko WT, Hiramoto RN, et al. 31P NMR spectroscopy in vivo of tumours. JMgn Res 1982; 49: 271-86. 1. Zon G, Brandt JA, Egan W. Brief Communication: Determination of enantiomeric homogeneity (optical purity) of cyclophosphamide by nuclear magnetic resonance spectroscopy, J Natl Cancer Inst 1977; 58: 1117.
4.
P. HILGARD
J. ENGEL
N, Pohl J, Stekar J. Studies on the urotoxicity of oxazaphosphorine cytostatics and its prevention I Experimental studies on the urotoxicity of alkylating compounds. Europ JCancer 1981: 17: 595-607 3. Schnitker J. Uroprotektion mit Mesna bei der Chemotherapie maligner Tumoren mit Oxazaphosphorinen. Biometrische Auswertung einer sequentiellen klinischen Prufung. ArzneimForsch/Drug Res 1982, 32: 1334-38.
to
change in
pH.
70% of its
previous value.
There
was no
significant
Ng et al found that tumours in animals showed a decrease in the areas of their PCr peaks as they developed, possibly because a large of tumour cells became anoxic or hypoxic. PCr is an energy compound which can donate a phosphoryl residue to ATP when the ATP/ADP ratio falls; the equilibria of these reactions are such that the ATP concentration is maintained until almost no PCr is present. Thus the PCr peak will be a sensitive index of tissue metabolic state. After successful treatment by chemotherapy the tumour PCr peaks increased again in size.4 In the light of these animal data the fall in the PCr integral relative to those of the other peaks suggests that doxorubicin therapy was unsuccessful (or only partly successful) and that the tumour was developing. This is in accord with the clinical picture: the tumour did not decrease in size and the patient’s condition worsened after the second NMR examination, causing a third examination to be cancelled. It is at present very difficult to study human tumours in situ by NMR since few occur in accessible positions on the limbs. This case represented a rare (and, so far, unique) opportunity to study the evolution of a tumour and its response to chemotherapy. As further clinical experience becomes available NMR will help not only in the management of patients but also in giving a sense of direction to the biochemical study and the rational treatment of experimentally induced tumours in animals. mass
storage
We thank the Cancer Research Campaign, Science and Engineering Research Council, Action Research for the Crippled Child, Muscular Dystrophy Group of Great Britain, Special Trustees of University College Hospital, and the Wellcome Trust for financial support.
Department of Biochemistry, St George’s Hospital Medical School, London SW 17 0RE
J. R. GRIFFITHS
Department of Medical Physics and Bio-engineering, School of Medicine, University College London
E. CADY
Department of Medicine, School of Medicine, University College London
R. H. T. EDWARDS
Department of Nuclear Medicine, The Royal Marsden Hospital, Sutton
V. R. MCCREADY
Department of Physiology, University College London
Royal Marsden Hospital, London
D. R. WILKIE E. WILTSHAW
BIOACTIVITY OF CYCLOPHOSPHAMIDE PREPARATIONS
SIR,-Dr Shaw and colleagues (March 26, p 709) suggested that the ’Endoxana’ brand of cyclophosphamide (WB Pharmaceuticals) was more active in man and laboratory animals than the generic cyclophosphamide preparation from Farmitalia Carlo Erba. On the basis of differences in the intensity of several fragment ions in the mass spectrum these workers suggested that the two preparations might differ in their content of the two enantiomers of
cyclophosphamide. We have measured the optical activity of several samples of these cyclophosphamide preparations and repeatedly confirmed that for both compounds the optical rotation, at different wavelengths, is I zero-ie, both cyclophosphamides are identical racemic mixtures. Mass spectroscopy by fast atom bombardment or field desorption ionisation techniques revealed no differences in the chemical composition of the two preparations. However, electron impact spectra revealed minor quantitative variations which were caused by thermal rearrangement reactions during evaporation which, in turn, were related to the different crystal sizes of the two two
cyclophosphamides. If the samples were dissolved in water and the solvent subsequently evaporated within the mass spectrometer mlet system, the spectra of the two cyclophosphamides became identical. In addition, thermogravimetric analysis of both drugs resulted in superimposable curves, suggesting not only equal water contents in the two preparations but also, once again, chemical identity, Together with the identities of the nuclear magnetic resonance spectra and of the gas/liquid chromatography data, reported by Shaw et al, our findings clearly indicate that the two drugs are chemically alike. Minor difference between the two-eg, in crystal structure, storage times, and dissolution procedures-would probably not show up in pharmacological and toxicological tests. Since the starting point of Shaw and colleagues’ investigation was a clinical observation suggesting higher bladder toxicity of endoxana we have done some rat bladder toxicity assays.2Unlike Shaw et al we found no differences between the two compounds, provided the doses were adjusted to anhydrous cyclophosphamide, The dose/toxicity relationship after a single administration was identical. Equally, daily doses of 50 mg/kg of either preparation produced the same quantitative changes in the rat bladder. In addition, the spleen weights in all treated animals were dosedependently reduced, regardless of the cyclophosphamide preparation used. Thus WB Pharmaceuticals and Farmitalia Carlo Erba cyclophosphamide are by current analytical standards identical chemical entities and consequently possess the same pharmacological and toxicological profiles. Since its introduction into clinical practice by Asta-Werke 25 years ago, ’Endoxan’ (UK trade mark endoxana) has been related to anhydrous cyclophosphamide so that, for example, a 1 g vial contains 1069 mg monohydrate, corresponding to 1 g anhydrous active material. In contrast, the Farmitalia Carlo Erba product is specified on the basis of the monohydrate-ie, a 1 g vial contains only 936 mg of the active ingredient. Thus, although both products are declared as "I g cyclophosphamide", one contains 6-4% less active substance than the other. This may be clinically insignificant in low dose ranges, but with high cyclophosphamide treatment schedules, such as those mentioned by Shaw et al, the patient will probably receive more than 1 g cyclophosphamide less per treatment course if treated with the Farmitalia Carlo Erba drug. Cyclophosphamide induced bladder toxicity in man has a steep dose/toxicity curve, and the higher incidence of haemorrhagic cystitis following endoxana treatment could be explained solely by the higher dose administered. Bladder toxicity, even after ultrahIgh .doses of cyclophosphamide, can be effectively controlled by the simultaneous administration of adequate mesna doses;3however, differences in the therapeutic efficacy of the two cyclophosphamides are likely to occur and would definitively require dose adjustments. The extensive clinical experience with cyclophosphamide of the past three decades was exclusively based on endoxana, and all dose recommendations which have emerged from worldwide clinical research activities refer to the active (anhydrous) drug. Since all cytotoxic drugs have comparatively low therapeutic indices, the dose-specifications have to be exact and clear; generics should be matched with the original drug to avoid confusing doctors. pharmacists, and nurses and to maintain the comparability of clinical data. Asta-Werke AG, Degussa Pharma Gruppe, D-4800 Bielefeld 14, West Germany
U. NIEMEYER
Department of Physical Chemistry, Degussa Wolfgang, Hanau, West Germany
E. BUSKER
WB Pharmaceuticals Ltd, Bracknell, Berkshire
J. DALTON
2. Brock
Ng TC, Evanochko WT, Hiramoto RN, et al. 31P NMR spectroscopy in vivo of tumours. JMgn Res 1982; 49: 271-86. 1. Zon G, Brandt JA, Egan W. Brief Communication: Determination of enantiomeric homogeneity (optical purity) of cyclophosphamide by nuclear magnetic resonance spectroscopy, J Natl Cancer Inst 1977; 58: 1117.
4.
P. HILGARD
J. ENGEL
N, Pohl J, Stekar J. Studies on the urotoxicity of oxazaphosphorine cytostatics and its prevention I Experimental studies on the urotoxicity of alkylating compounds. Europ JCancer 1981: 17: 595-607 3. Schnitker J. Uroprotektion mit Mesna bei der Chemotherapie maligner Tumoren mit Oxazaphosphorinen. Biometrische Auswertung einer sequentiellen klinischen Prufung. ArzneimForsch/Drug Res 1982, 32: 1334-38.