Interferons--expanding therapeutic roles

PASylation Enhances the Stability, Potency, and Plasma Half-Life of Interferon α-2a: A Molecular Dynamics Simulation

In this study, the effectiveness of PASylation in enhancing the potency and plasma half-life of pharmaceutical proteins has been accredited as an alternative technique to the conventional methods such as PEGylation. Proline, alanine, and serine (PAS) chain has shown some advantages including biodegradability improvement and plasma half-life enhancement while lacking immunogenicity or toxicity. Although some experimental studies have been performed to find the mechanism behind PASylation, the detailed mechanism of PAS effects on the pharmaceutical proteins has remained obscure, especially at the molecular level. In this study, the interaction of interferon α-2a (IFN) and PAS chain is investigated using molecular dynamics simulation method. Several important parameters including secondary structure, root-mean-square distance, and solvent accessible surface area to investigate the stability, bioavailability, and bioactivity of the PASylated protein are studied. The results demonstrate that IFN conformation is not affected critically through PASylation while it results in improvement of the protein stability and bioactivity. Therefore, PASylation can be considered as a proper biological alternative technique to increase the plasma half-life of the biopharmaceutical proteins through enlarging apparent volume. The proposed simulation represents a computational approach that would provide a basis for the study of PASylated pharmaceutical proteins for different future applications.

Pegylated interferon-alpha plus taurine in treatment of rat liver fibrosis

AIM: To investigate the antifibrotic effects of peginterferon-alpha 2b and taurine on oxidative stress markers and hepatocellular apoptosis.

METHODS: Sixty rats with CCl4-induced liver fibrosis were divided into 4 groups (n = 15). Group 1 was left for spontaneous recovery (SR). Groups 2-4 received peginterferon-alpha 2b, taurine, and their combination, respectively, for four weeks. Histological fibrosis scores, histomorphometric analysis, tissue hydroxyproline, tissue MDA, GPx and SOD activities were determined. Activated stellate cells and hepatocellular apoptosis were also evaluated.

RESULTS: The degree of fibrosis decreased in all treatment groups compared to spontaneous recovery group. Taurine alone and in combination with peginterferon-alpha 2b reduced oxidative stress markers, but peginterferon-alpha 2b alone did not. Apoptotic hepatocytes and activated stellate cells were higher in groups 2-4 than in group 1. Combined taurine and peginterferon-alpha 2b further reduced fibrosis and increased activated stellate cell apoptosis, but could not improve oxidative stress more than taurine alone.

CONCLUSION: Peginterferon-alpha 2b exerts anti-fibrotic effects on rat liver fibrosis. It seems ineffective against oxidative stress in vivo. Peginterferon-alpha 2b in combination with taurine seems to be an antifibrotic strategy.

Induction of cell cycle arrest and apoptosis by a combined treatment with 13-cis-retinoic acid, interferon-α2a, and α-tocopherol in squamous cell carcinoma of the head and neck

BACKGROUND

We have previously conducted phase II trials with a combination of 13-cis-retinoic acid (13-cRA), interferon-alpha2a (IFN-alpha2a), and alpha-tocopherol (alpha-TF) in patients with advanced oral premalignant lesions and locally advanced head and neck cancer in the adjuvant settings and achieved promising outcomes. The present study was conducted in vitro to elucidate the mechanisms of anti-tumor activity of this 3-drug combination in squamous cell carcinoma of the head and neck (SCCHN).

METHODS

Five SCCHN cell lines were treated with 13-cRA, IFN-alpha2a, and alpha-TF as single agents or 2- to 3-drug combinations for 72 hours. Inhibition of cell growth and cell cycle progression and induction of apoptosis by the treatments were evaluated.

RESULTS

Our results demonstrated that although each single-agent and 2-drug combination showed a certain level of cell growth inhibition, the 3-drug combination apparently further inhibited cell growth in comparison to any single agents and 2-drug combinations in the 5 SCCHN cell lines. Cell cycle analysis on Tu212 and 886LN cells by flow cytometry exhibited significant accumulation of the cells at S phase in the 3-drug combination. On the other hand, Annexin-V binding assay demonstrated that the 3-drug combination induced more profound apoptosis than any of the single agents or 2-drug combinations. In parallel, proteolytic cleavages of pro-caspase-8, -9, -3 and poly (ADP ribose) polymerase as well as caspase-3 activity induced by the 3-drug treatment were observed.

CONCLUSIONS

Our data suggests that 3-drug combination biochemopreventive regimen has cooperative inhibitory effect on the growth of SCCHN cells. Both cell cycle arrest and apoptosis contribute to cell growth inhibition of this 3-drug combination therapy.

Interferon-alpha inhibits interleukin-3-induced proliferation of Ba/F3 cells in a protein kinase R-dependent manner

We have previously shown that interferon-alpha (IFN-alpha) inhibits proliferation of Ba/F3 cells by interfering with the action of the mitogen interleukin-3 (IL-3) [Cell Signal 11 (1999) 769]. Here, we have characterised the role of protein kinase R (PKR), an IFN-alpha-inducible enzyme, in the mediation of IL-3-antagonistic IFN-alpha effects. Downregulation of PKR expression by antisense oligonucleotide treatment blocked IFN-alpha-induced growth inhibition. Reduction of PKR levels and overexpression of a dominant-negative PKR mutant correlated with diminished inhibitory IFN-alpha effects on the IL-3-dependent expression of a luciferase reporter construct, GAS-luc. Furthermore, increased nuclear levels of STAT1 (bound in ISGF3 complexes) were observed in PKR-depleted cells cultured with or without IFN-alpha. Together, our data indicate an essential role of PKR in the mediation of IL-3-antagonistic IFN-alpha effects on Ba/F3 cells. They also suggests that activation of STAT1, an essential mediator of IFN effects, is insufficient for growth inhibition if PKR is not expressed.

Interferon-induced Raynaud's syndrome

OBJECTIVE

To review the clinical features, diagnosis, treatment, and outcome of interferon-induced Raynaud's phenomenon.

METHODS

The medical literature was reviewed from 1967 to November 2001 with the assistance of a MEDLINE search using the key words: Raynaud, Interferon, ischemia, thrombosis and necrosis. A qualitative review was performed after the articles were abstracted and the relevant information was summarized.

RESULTS

Twenty-four cases of interferon-induced Raynaud's phenomenon (including our patient) are described. Interpheron-alpha was the most common causative agent (14 cases). The symptoms appeared weeks to years after beginning treatment and varied from mild vasospasm to occlusion of digital arteries and tissue necrosis (14 cases), sometimes necessitating finger amputation (6 patients). Digital plethysmography, arteriography and capillaroscopy were valuable diagnostic tools. In 4 cases, cardiac, ophthalmic, or central nervous system drug-induced ischemia accompanied the peripheral Raynaud's phenomenon. Of the 15 cases with a documented outcome, withdrawal of the drug alone resulted in complete (6 patients) or partial (1 patient) recovery. In the others, supportive therapy was needed. The recovery period lasted from 2 weeks to 3 months. In 2 patients, continuation of treatment was possible.

CONCLUSIONS

Raynaud's phenomenon and related complications must be recognized as possible side effects of interferon therapy. Early diagnosis and withdrawal of the drug may prevent unnecessary morbidity and disability.

Interferon-alpha inhibits cell cycle progression by Ba/F3 cells through the antagonisation of interleukin-3 effects on key regulators of G(1)/S transition

The molecular mechanisms of interferon-alpha (IFN-alpha)-mediated cell growth inhibition are incompletely understood. Here, we have analysed how IFN-alpha interferes with the interleukin-3 (IL-3)-stimulated cell cycle progression by Ba/F3 cells. The antiproliferative cytokine caused a delay in cell cycle progression, which correlated with a diminished activation of the cyclin-dependent kinases 2 and 4 in IL-3-stimulated cells. While IFN-alpha did not affect the expression of p27(Kip1) and p21(Waf1), it efficiently inhibited the IL-3-induced expression of D-type cyclin and cyclin E proteins. No IL-3-antagonistic effects of the IFN, however, were observed at the mRNA level of cyclin expression. Furthermore, IFN-alpha suppressed the IL-3-induced release of E2F transcription factors from the retinoblastoma protein (pRb) and enhanced pRb-mediated transcriptional repression. The growth factor-antagonistic action of IFN-alpha correlated with a strong stimulation of protein kinase R expression, suggesting that inhibition of protein synthesis plays a pivotal role in IFN-alpha-mediated inhibition of cell cycle progression.

Potential new therapeutic options in Behçet's syndrome

Behçet's syndrome is a multisystem disorder that causes orogenital ulceration, skin lesions and intraocular inflammation with uveitis and retinal vasculitis. A proportion of affected individuals also develop vascular and central nervous system manifestations, with significant morbidity and mortality. Although the aetiopathogenesis of Behçet's syndrome is poorly understood, the condition is considered to be driven, at least in part, by autoimmune mechanisms. Conventional therapy relies on available anti-inflammatory and immunomodulatory agents, and, in view of the paucity of controlled clinical trials, it is to a large extent empirical. Oral ulcers can often be treated by topical application of corticosteroids. In addition to corticosteroids, agents used to treat ocular inflammation and significant systemic manifestations include colchicine, thalidomide, azathioprine, mycophenolate mofetil, cyclosporin, tacrolimus, cyclophosphamide and chlorambucil. The response to these agents is variable and there is a distinct need for more effective rational treatment. Over the last decade, a number of open studies have produced promising results using recombinant interferon-alpha preparations. Evaluating, in a methodical manner, the other new biological agents that are becoming available for the treatment of inflammatory diseases offers great promise, not only for effective management but also for providing insights into aetiopathogenesis.

Interferon-induced gene expression and signaling in human hepatoma cell lines

BACKGROUND/AIM

Interferon(IFN)-alpha alone or combined with other antiviral substances has been extensively used for the treatment of viral infections of the liver. Since the molecular mechanisms of IFN action in liver cells are relatively poorly characterized, we studied IFN-induced gene expression and signaling in human hepatoma, HepG2 and HuH7 cell lines.

METHODS/RESULTS

IFN binding to its specific cell surface receptor leads to activation of the Janus family tyrosine kinase (JAK) - signal transducer and activator of transcription (STAT) pathway. We observed that in HepG2 and HuH7 cells IFN-inducible genes were upregulated by IFNs, but relatively high concentrations of IFN-alpha were needed to turn on MxA (an antiviral gene) and MxB gene expression. The basal expression of IFN-alpha receptor (IFNAR1 and IF-NAR2) JAK1 and TYK2 mRNAs was readily detectable, and their expression was not significantly altered by treatment with either IFN-alpha or IFN-gamma. Hepatoma cells possessed relatively low basal expression levels of IFN signaling molecules STAT1, STAT2 and p48, but their expression was strongly upregulated by both types of IFNs. Pretreatment of HepG2 or HuH7 with low IFN-gamma doses, followed by stimulation with IFN-alpha, resulted in a marked enhancement of the formation of IFN-alpha-specific signaling complex ISGF3.

CONCLUSION

The results indicate positive feedback mechanisms in the IFN signaling system in hepatoma cells.

Interferon-alpha inhibits proliferation of Ba/F3 cells by interfering with interleukin-3 action

Interferons (IFNs) are potent inhibitors of cell proliferation that are used for the treatment of several haematological malignancies. The mechanisms through which IFNs exert their antiproliferative effects on target cells, however, are largely unknown. Here we show that IFN-alpha, in murine Ba/F3 cells, directly interferes with the action of the essential mitogen interleukin (IL)-3. In transiently transfected Ba/F3 cells, IFN-alpha efficiently inhibited the IL-3-stimulated expression of a luciferase reporter construct, GAS-luc, that is activated through the JAK2/STAT5 pathway. Electrophoretic mobility shift assays and Northern blot experiments, however, revealed that neither the IL-3-induced DNA binding of STAT5 nor the transcription of the STAT5-dependent genes oncostatin-M, pim-1 and c-fos were suppressed by IFN-alpha, suggesting that the diminished expression of the luciferase protein was due to a direct inhibition of IL-3-stimulated protein synthesis. This hypothesis was supported by the observation that IFN-alpha, even though it had no effect on the transcription of the c-fos gene, efficiently suppressed the IL-3-dependent expression of the c-Fos protein. Furthermore, our results indicate that IFN-alpha induced an overexpression of the double-stranded RNA-activated protein kinase (PKR), an enzyme that inhibits protein synthesis through the phosphorylation and inactivation of the eukaryotic initiation factor-2. Therefore, we hypothesize that IFN-alpha, in Ba/F3 cells, interrupts IL-3-dependent mitogenic signals, at least in part, through the suppression of protein synthesis and that induction of PKR activity may play a pivotal role in this process.

Role of STAT5 in interferon-alpha signal transduction in Ba/F3 cells

In interferon-alpha (IFN-alpha) signalling, the essential role of the transcription factors STAT1 and STAT2 is well established. In contrast, the involvement of other STAT proteins, including STAT5, is much less well understood. Here we show that, in IFN-alpha-responsive Ba/F3 cells, this cytokine stimulates the DNA-binding of STAT5A and B but that IL-3 is a much more potent activator of both STAT5 isoforms. A stably expressed dominant-negative mutant of JAK2 suppressed the IL-3- but not the IFN-alpha-dependent DNA binding of STAT5, suggesting independent mechanisms of its activation. Northern blots revealed that IL-3 strongly induced the expression of two STAT5-regulated genes, pim-1 and oncostatin-M, whereas IFN-alpha had a weak stimulatory effect on pim-1 expression only. In summary our results suggest that, despite the capability of IFN-alpha to stimulate DNA binding of STAT5, this transcription factor does not play a pivotal role in IFN-alpha signalling in Ba/F3 cells.

Effect of type I interferon on experimental autoimmune uveoretinitis in rats

In order to establish a scientific basis for the potential use of type I interferons (IFNs) in clinical uveitis, we examined the effect of a preparation of IFN-alpha/beta on experimental autoimmune uveoretinitis (EAU). Lewis rats were immunized with bovine interphotoreceptor retinoid-binding protein (IRBP) and given daily intramuscular injections of 10(5) IU mouse natural IFN-alpha/beta. Intraocular inflammation was assessed by slit-lamp biomicroscopy and histopathological examination. Rats treated daily with IFN-alpha/beta starting on the day of IRBP immunization showed decreased intraocular inflammation as well as a slight delay in onset of inflammation when compared to control rats. This effect was also observed to a lesser extent in rats treated during either the induction phase of EAU only, or starting immediately after the onset of inflammation in the effector phase of EAU. Measurement of IRBP-stimulated splenocyte proliferation and serum anti-IRBP antibody subtypes did not reveal a significant difference between IFN-alpha/beta-treated rats and control rats. Measurement of cytokine production by IRBP-stimulated splenocytes in vitro showed significantly decreased TNF-alpha for IFN-alpha/beta-treated rats compared to control, but no difference for IFN-gamma, IL-2, IL-4, and IL-10. These results indicate that systemic administration of IFN-alpha/beta suppresses IRBP-induced EAU in rats, and suggest that such suppression may be mediated in part by a reduction in TNF-alpha production.

Spontaneous and inducible cytokine responses in healthy humans receiving a single dose of IFN-alpha2b: increased production of interleukin-1 receptor antagonist and suppression of IL-1-induced IL-8

The present study was to determine whether the administration of a single dose of interferon-alpha2B (IFN-alpha2B) to healthy humans affects endogenous (or basal level) or inducible cytokines in a whole blood, ex vivo culture. Twenty-four healthy volunteers received an s.c. injection of IFN-alpha2b (3 x 10(6)U), and 4 volunteers received the vehicle as placebo. The study was blinded. Blood was drawn before and 3, 6, 12, and 24 h after the injection and incubated in the presence or absence of lipopolysaccharide (LPS) or interleukin-1beta (IL-1beta). After 24 hs, the plasma was assayed for tumor necrosis factor-alpha (TNF-alpha), IFN-gamma, IL-1beta, IL-1 receptor antagonist (IL-1Ra), and IL-8. Treatment with IFN-alpha2b was associated with a 4.8-fold increase in the endogenous production of IL-1Ra in cultured blood sustained over 24 hs. In contrast, no change in endogenous IL-1Ra production was detected in the controls. A significant suppression (75%, p < 0.001) of IL-1beta-induced IL-8 production 3 and 6 h after IFN-alpha2b compared with control subjects was observed. These effects were also observed when IFN-alpha2b was added directly to whole blood cultures in vitro. In contrast to IL-1 stimulation, LPS stimulation of blood from IFN-alpha2b-treated subjects resulted in enhanced IL-1beta and TNF-alpha production. These results suggest that a single dose of IFN-alpha2b induces an anti-inflammatory state for endogenous stimuli but a proinflammatory state for exogenous endotoxin.

Constitutive expression of interferon beta in differentiated epithelial cells exposed to environmental stimuli

The body's first line of defense against external challenge are the epithelial cells that line the skin and the respiratory, digestive, and genitourinary tracts. Inasmuch as interferon-beta (IFN-beta) participates in host defense against viral, bacterial, and parasitic infections and tumors, we hypothesized that this secreted protein is expressed in various murine epithelial cell types that line portals of entry to the body. We used immunohistochemistry and in situ hybridization techniques to measure IFN-beta expression in the various epithelial cell types and in internal murine organs sheltered from environmental stimuli. The epithelial cell types lining the skin, digestive tract, urinary tract, reproductive tract, and upper respiratory tract constitutively expressed IFN-beta. Specifically, all differentiated epithelial cells at risk of environmental exposure expressed IFN-beta (protein and mRNA) with the exception of the ciliated epithelial cells lining the lower respiratory tract. Epithelial cells of internal organs that are not directly exposed to external pathogens did not express IFN-beta.

Regulation of IRF and STAT gene expression by retinoic acid

Retinoic acid has antiproliferative and differentiative effects on many cell types. However, the molecular mechanisms involved in ATRA (all-trans retinoic acid) -dependent growth inhibition and cell differentiation are poorly understood. On the other hand, several different cytokine specific transcription factors such as signal transducers and activators of transcription (STAT) and interferon regulatory factors (IRF) are known to be instrumental in mediating differentiative, growth regulatory and antiproliferative effects in cells. The IRF family consists of six different proteins, of which IRF-1 has been demonstrated to have antiproliferative and tumor suppressive functions. We have shown that ATRA activates IRF-1 gene expression in several myeloid leukemia cell lines (HL-60, NB4, THP-1, U937), all of which respond to ATRA by growth inhibition. In addition, during ATRA-induced myeloid differentiation, gene expression of STAT1, STAT2, and p48 was upregulated. These proteins are involved in IFN-alpha specific signaling. ATRA-induced expression of IRF and/or STAT transcription factors may be one of the molecular mechanisms mediating growth inhibition by ATRA.

Pharmacotherapeutics of Biotechnology-Derived Products

Biotechnology has contributed to important advances in the healthcare field. Products include various hormones, enzymes, cytokines, vaccines, and monoclonal antibodies, with use in diverse therapeutic areas. The majority of approved biotechnology-derived therapeutic products are recombinant proteins. Many have orphan drug status and, therefore, are used in relatively small patient populations. Newer generation biotechnology products are likely to include small molecules, gene therapy products, and increased numbers of vaccines and monoclonal antibody products. Biotechnology provides the means to develop diverse, innovative, and effective approaches to the prevention, treatment, and cure of human disease.

The three-dimensional high resolution structure of human interferon alpha-2a determined by heteronuclear NMR spectroscopy in solution

The solution structure of recombinant human interferon alpha-2a (Roferon-A) has been determined by multidimensional heteronuclear NMR spectroscopy. The calculations using simulated annealing produced a family of 24 convergent structures which satisfy the experimental restraints comprising 1541 NOE-derived inter-proton distances, 187 dihedral restraints, 66 pairs of hydrogen bond restraints, and six upper and lower limits for two disulfide bridges. The fractional labeling of methyl groups allowed their direct and unambiguous stereospecific assignment which proved to be essential for obtaining a high resolution of the structures. A best fit superposition of residues 10 to 47, 50 to 101 and 111 to 157 gives an rms deviation of 0.62 A for the backbone heavy atoms and 1.39 A for all heavy atoms of these segments. The dominant feature of the structure is a cluster of five alpha-helices, four of which are arranged to form a left-handed helix bundle with an up-up-down-down topology and two over-hand connections. The interpretation of heteronuclear 15N-¿1H¿ NOE data shows the co-existence of flexible regions within an otherwise rigid framework of the protein. Four stretches of pronounced flexibility can be located: Cys1-Ser8, Gly44-Ala50, Ile100-Lys112, and Ser160-Glu165. Among the structurally related four-helical bundle cytokines, the structure of IFN alpha-2a is most similar to that of human interferon alpha-2b and murine interferon-beta. From this structural information and mutagenesis data, areas on the surface of the protein are identified which seem to be important in receptor interactions.

The management of genital condylomas, intraepithelial neoplasia, and vulvodynia

The natural history of HPV-related disease still is poorly understood. Screening of apparently healthy populations suggests that most HPV exposure results only in latent infection; that is, there is no active HPV DNA replication, but the HPV copy number is held at a steady state because viral replication parallels cell division. Unfortunately, knowledge of the cell-virus interaction and the host-immune response has not yet provided an effective medical therapy or a preventive vaccine. Rather, the management of HPV-induced disease remains rooted to the strategy of repeated local destruction. The physician should work methodically through a series of strategic decisions before committing to a management plan.

Clinical relevance of all-trans retinoic acid pharmacokinetics and its modulation in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is uniquely sensitive to treatment with all-trans retinoic acid (ATRA) which exerts its action via a well-documented cytodifferentiating mechanism. The combination of this retinoid with anthracyclines gives high percentages of complete remission and is now considered the optimal induction treatment for APL patients. Continuous treatment with ATRA, however, induces accelerated drug catabolism, with progressive decline in plasma drug concentrations potentially to below the levels required to maintain differentiation of leukemic cells. This process, which occurs rapidly and consistently has led to the hypothesis that the development of acquired clinical resistance to ATRA in APL has a pharmacologic basis. The rapid autoinduction of the hypercatabolic state precludes maintenance with continuous ATRA oral dosing, and is a limitation of better use of the drug both in APL and in other disorders in which it could be beneficial. Here we briefly review the pharmacologic alterations of ATRA metabolism induced by continuous oral administration, the clinical implications of this phenomenon, and the strategies currently under investigation to prevent or overcome the induced catabolism of this retinoid.

Interferon-alpha and its effects on the cytokine cascade: a pro- and anti-inflammatory cytokine

Interferon-alpha (IFN alpha) has emerged as an important regulator of growth and differentiation, affecting cellular communication and signal transduction pathways as well as immunological control. The efficacy of IFN alpha has been demonstrated in many different diseases of viral, malignant, angiogenic, allergic, inflammatory, and fibrotic origin. Cytokines are pleiotropic and redundant molecules showing a wide variety of biologic functions on various tissues and cells, and several different cytokines exert similar and overlapping functions on certain cells. Data gained in the last years support this view also for IFN alpha. Initially thought to have mainly immunomodulating and proinflammatory effects, recent data suggest that IFN alpha has several anti-inflammatory properties. These newly identified anti-inflammatory and immunosuppressive functions may help to explain some of the IFN mechanisms.

The role of interferon in the therapy of malignant lymphoma

As a single agent, interferon-alpha (IFN-alpha) can induce remissions, mostly partial, in a large fraction of patients with indolent lymphomas, including the low grade B-cell lymphomas and cutaneous T-cell lymphoma. In aggressive lymphomas, IFN has minimal activity, and in Hodgkin's disease the limited available experience suggests only modest activity. In indolent B-cell lymphomas, IFN has been integrated with chemotherapy in several large trials: the majority of these trials indicate a favorable impact on failure-free survival; a survival benefit of IFN has been reported by the French-Belgian group. Updated results are now available from a previously reported trial from the MD Anderson Cancer Center that also indicate an apparent survival benefit when IFN is used in conjunction with chemotherapy in patients with indolent B-cell lymphoma.

Aggressive Course of Angiofibroma in an HIV-Positive Patient

We report nasopharyngeal angiofibroma in a 13 year old boy treated with embolization, surgical excision and radiotherapy, which recurred 13 years later. No features of sarcomatous transformation were found, but the tumor had a locally aggressive course, possibly due to the HIV-posltivity of the patient who then died of AIDS. The relations between the clinical course of the tumor and severe immunodeficiency are discussed.

Phase II trial of 13-cis-retinoic acid plus interferon-alpha in recurrent head and neck cancer

13-cis-retinoic acid (isotretinoin) and interferon-alpha have limited activity as single agents in advanced cancer. Preclinical data indicate that these agents have different mechanisms of action and, in combination have greater activity (that is, the ability to modulate growth and differentiation) in a number of malignant cell types than either agent alone. In clinical trials, the new biological regimen of 13-cis-retinoic acid and interferon-alpha was shown to have major activity in advanced squamous cell carcinoma of the skin and cervix. We conducted a phase II trial of this regimen in recurrent squamous cell carcinoma of the head and neck. Of the 21 evaluable patients, none had a complete response, and only one had a partial response (5%). Two patients had minor responses, four had stable disease, and 14 experienced disease progression. Five patients developed grade 3 toxic effects, including skin toxicity, fatigue, headache, and anorexia/weight loss. The median survival duration was 25.5 weeks (range, 4-95). The combination of 13-cis-retinoic acid and interferon-alpha at this dose and schedule is ineffective for the treatment of recurrent squamous cell carcinoma of the head and neck.

Retinoic acid and interferon combination studies in human cancer

Retinoic acid and interferon-alpha have limited single-agent activity in advanced cancer. Cell culture data indicate that in combination these agents have enhanced activity (modulating growth and differentiation) in a number of malignant cell types. Recent clinical work in advanced squamous cell carcinoma reports major activity with this regimen. This paper reviews the preclinical and clinical data testing retinoic acid in combination with interferons and presents recent work integrating these agents with radiotherapy in locally advanced cervical cancer.

Pharmacokinetics of an extended-release human interferon alpha-2b formulation

The in vivo half-life of human interferon alpha-2b (hIFN-alpha-2b) is relatively short, and frequent injections over prolonged periods are required for efficacy. An extended-release formulation of hIFN-alpha-2b (Depo/IFN) was created by encapsulation into a lipid-based drug-delivery system. The capture efficiency was 51% +/- 13% and the release half-life in human plasma at 37 degrees C was 16 days. The pharmacokinetics of Depo/IFN was compared with that of unencapsulated standard hIFN-alpha-2b (Std/IFN) in the peritoneal cavity of male BDF1 mice. Depo/IFN exhibited a 13-fold longer intraperitoneal (i.p.) half-life as compared with Std/IFN (20 vs 1.5 h). The release of free hIFN-alpha-2b from Depo/IFN into the peritoneal cavity was slow and protracted, with a 10-fold lower peak concentration and a 13-fold longer apparent half-life being observed in comparison with Std/IFN. The areas under the curve of free hIFN-alpha-2b in the peritoneal cavity were comparable for Depo/IFN and Std/IFN. hIFN-alpha-2b was detectable in plasma only after the i.p. administration of Std/IFN. These data suggest the possibility that Depo/IFN may be useful as an extended-release formulation of hIFN-alpha-2b.