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A trial of SGN-00101 (HspE7) to treat high-grade anal intraepithelial neoplasia in HIV-positive individuals, men & women

“…..This is the first reported study of a therapeutic vaccine directed against HPV antigens to treat HG-AIN in HIV-positive individuals….â€

AIDS: Volume 20(8) 12 May 2006 p 1151-1155

[CLINICAL SCIENCE: CONCISE COMMUNICATION]

Palefsky, Ma,d; Berry, J a; Jay, Naomia; Krogstad, aa; Da Costa, a; Darragh, Mb; Lee, Jeannette Yc,d

From the aDepartment of Medicine, University of California, San Francisco, California, USA

bDepartment of Pathology, University of California, San Francisco, California, USA

cDepartment of Medicine, University of Alabama at Birmingham, Alabama, USA

dAIDS Malignancy Consortium.

Abstract

Objectives: To test a therapeutic vaccine consisting of a fusion of the human papillomavirus (HPV) 16 E7 protein and the Mycobacterium bovis heat shock protein 65 (SGN-00101) to treat high-grade anal intraepithelial neoplasia (HG-AIN) in HIV-positive individuals.

Design: A phase I/II trial with three cohorts of five participants each, sequentially assigned to receive 100, 500 or 1000 μg SGN-00101, injected three times subcutaneously in alternating thighs at 4-week intervals. Anal disease was assessed at baseline, 8, 12, 24 and 48 weeks and was classified as the more severe of anal cytology and anal biopsy. Anal HPV DNA was detected using L1 consensus primer-based PCR followed by type-specific probing and dot-blot hybridization (DBH). HPV16, 18 and 31 DNA copy numbers were measured using quantitative real-time PCR.

Setting: University-based research clinic.

Participants: Thirteen HIV-positive men and two HIV-positive women with HG-AIN.

Results: There were no drug-related serious adverse events or significant changes in HIV viral load and CD4/CD8 ratio. At 48 weeks, two of five participants in both the 100 and 500 μg cohorts regressed to AIN 1 and one of five participants in the 1000 μg cohort regressed to atypical squamous cells of undetermined significance (ASC-US). All participants had at least one oncogenic HPV type at baseline. Three of five (60%) participants who regressed to AIN 1 or ASC-US became HPV-negative using DBH and real-time PCR, compared with none of 10 participants with no clinical response (P = 0.02).

Conclusions: SGN-00101 was well tolerated in HIV-positive individuals, with preliminary evidence for clinical activity.

Introduction

The incidence of anal cancer is increased in men who have sex with men (MSM) compared with men in the general population and is even higher among HIV-positive MSM than among HIV-negative MSM [1]. Since 1996 when HAART was introduced, the incidence of anal cancer has continued to increase [2]. Anal cancer has many biological similarities to cervical cancer, including a strong association with human papillomavirus (HPV) infection, primarily HPV16 [3]. Cervical cancer is preceded by cervical intraepithelial neoplasia (CIN) 2-3. Likewise, anal intraepithelial neoplasia (AIN) 2-3, also known as high-grade AIN (HG-AIN), is a well-documented entity that has been shown to progress to invasive anal cancer [4]. HG-AIN is common among HIV-positive MSM and women [5].

Treatment of HG-AIN is expected to reduce the risk of progression to anal cancer but to date few treatment options for HG-AIN have been described. Surgical ablation had a high failure rate among HIV-positive men with extensive disease [5]. Options for treatment of more limited disease include infrared coagulation [6] and 85% trichloroacetic acid [5]. Therapeutic approaches that have low toxicity but allow for treatment of widespread or multifocal disease within the anal canal are clearly needed.

One approach that has not been well studied is the use of therapeutic vaccines targeted against HPV antigens. A phase I safety study of Zyc101, an encapsulated DNA plasmid vaccine showed safety and immunogenicity in HPV16-positive, HIV-negative men with HG-AIN [7]. No studies have been reported of a therapeutic vaccine in HIV-positive individuals.

HspE7 (SGN-00101, Stressgen Inc., , British Columbia, Canada) is a fusion protein of the HPV16 E7 protein with Mycobacterium bovis heat shock protein 65. The primary objective of this study was to test the safety of SGN-00101 to treat HG-AIN in HIV-positive individuals. Secondary objectives included assessment for histologic/cytologic regression of HG-AIN and the effect of SGN-00101 on anal HPV infection, HIV viral load (VL), and CD4 and CD8 T-cell counts.

Methods

All procedures were performed after obtaining informed consent and with the approval of the Committee on Human Research of the University of California, San Francisco (UCSF). HIV-positive men and women attending the UCSF Anal Neoplasia Clinic diagnosed with HG-AIN on biopsy between December 2002 and November 2003 were offered enrollment in the study. Inclusion criteria included being HIV-positive, ≥ 18 years of age; on a stable HAART regimen ≥ 4 weeks before study entry with no plan to change therapy during the study; HIV VL ≤ 500 copies/ml at enrollment; CD4 cell count ≥ 200/μl; histologic diagnosis of intra-anal or peri-anal HG-AIN within the past 90 days with residual HG-AIN confirmed by high resolution anoscopy (HRA) at enrollment. Participants must have declined routine surgical therapy or were not candidates for surgical excision of HG-AIN; agreed to contraception if participating in sexual activity that could lead to pregnancy; hemoglobin > 10g/dl; platelet count ≥ 75 000/μl; antineutrophil cytoplasmic antibody ≥ 1000/μl; serum creatinine < 1.5 × the upper limits of normal (ULN), and aspartate transaminase and alanine transaminase < 3 × ULN within 21 days of initiation of therapy. Exclusion criteria included immunocompromise for any reason other than HIV infection; taking immunostimulants; treatment of collagen-vascular or autoimmune disorder within the past 5 years; active serious opportunistic infections; history of anal or cervical cancer; concurrent high-grade CIN; life expectancy < 12 months; and history of severe allergic reactions (i.e., anaphylactic response) to drugs or any other allergen.

Participants were sequentially enrolled in three cohorts of five individuals each. Cohort 1 received 100 μg SGN-00101 subcutaneously in alternating thighs at baseline, 4 weeks and 8 weeks. Cohort 2 received 500 μg SGN-00101 and Cohort 3 received 1000 μg SGN-00101 according to the same schedule. Prior to entering participants on Cohorts 2 and 3, the AIDS Malignancy Consortium Data Safety and Monitoring Committee conducted a safety review and approved the enrollment of participants in these cohorts.

Anal cytology, HRA and anal biopsy were performed as described previously [8] at baseline, 8, 12, 24 and 48 weeks. The most severe grade of cytology and histology was used to determine AIN status. HIV VL, CD4 and CD8 cell counts were measured at baseline, 12 and 24 weeks. HPV testing was performed as described previously [9]. Briefly, PCR was performed on anal swab material using MY09/MY11 L1 consensus primers. The amplification product was probed with L1 consensus probes using dot-blot hybridization (DBH) and individually for 29 HPV types and a probe mix of 10 HPV types. Quantitative real-time PCR to measure HPV16, 18 and 31 DNA copy numbers was performed as described previously [10] on samples from participants positive at baseline for these types. HIV VL was measured using the Chiron branch chain assay with a limit of sensitivity of > 75 copies/ml.

Complete response (CR) was defined as regression to no AIN and partial response (PR) as regression to AIN 1. Descriptive statistics were used to summarize demographic, efficacy and safety data. Exact binomial confidence intervals were used to estimate proportions. Non-parametric methods, Wilcoxon Signed Rank Test and Kruskal-Willis Test were used to analyse continuous data.

Results

Twenty-two individuals with biopsy-proven HG-AIN were screened. Seven were excluded including three due to HIV VL above acceptable limits; one had oral Kaposi's sarcoma; one had AIN 1 only at study entry; one changed his mind; and one had a history of severe allergy. Of the 15 individuals enrolled, the mean age was 47.5 years. Fourteen (93%) were white and 13 (87%) were male. The mean Karnofsky performance status in Cohorts 1, 2 and 3 was 85%, 95% and 96%, respectively.

Overall SGN-00101 was well tolerated. The most common adverse events considered to be possibly or definitely related to the drug were injection site reactions in all 15 participants. Most were mild or moderate; only one severe reaction occurred after the second injection of one participant in Cohort 1. The average severity of the reactions increased with the dose administered, with all participants in Cohort 3 reporting moderate injection site reactions but the severity did not increase with each subsequent injection. The only other adverse events possibly or definitely related to the drug included insomnia (one participant), fever (one participant), rigors and chills (two participants), diaphoresis (three participants) and dizziness (two participants). All of these events were reported as mild.

Changes in AIN status after 48 weeks of study entry are shown in Table 1. Four (two each in Cohorts 1 and 2) of 15 participants (26%) showed regressed from HG-AIN to AIN 1 (PR). One participant in Cohort 3 regressed to atypical squamous cells of undetermined significance and was considered to have had a CR (7%). HG-AIN persisted in the other participants (no response).

Samples from 14 of 15 participants were adequate for HPV DNA analysis at baseline and all were positive for at least one oncogenic HPV type. A wide range of HPV types was detected. The most common was HPV58 in seven participants (50%), HPV16 in five participants (36%), and HPV18 in four participants (29%). Comparing baseline results with results at the final visit, one of five (20%) HPV16, five of seven (71%) HPV58 and two of four (50%) HPV18 infections were not detectable at the final visit using DBH. Clearance of HPV16, 18 or 31 indicated by DBH was confirmed using real-time PCR in all but two samples (Table 1). Three of five (60%) participants with CR or PR became HPV-negative by DBH and real-time PCR, compared with none of 10 participants with no response (P = 0.02). Among participants who showed no response, there was no clear pattern of HPV DNA copy number changes, with the HPV16, 18 or 31 copy number decreasing in some cases and increasing in others (data not shown).

Mean CD4, CD8 and HIV VL are shown in Table 2. The mean CD4 count declined by 80 cells/μl (P = 0.05) and the mean CD8 cell count declined by 187 cells/μl at week 24 (P = 0.04). However, the CD4/CD8 ratio remained unchanged (P = 0.23). There was no significant increase in mean HIV VL at 24 weeks and no increase at the higher dose levels.

Discussion

This is the first reported study of a therapeutic vaccine directed against HPV antigens to treat HG-AIN in HIV-positive individuals. Our results show that the vaccine is safe and well tolerated in these individuals. Studies from the pre-HAART era suggested that influenza vaccination could lead to an increased HIV VL [11]. However, later studies of individuals on effective HAART failed to show a vaccination-induced increase in HIV VL [12], similar to the present study. Although there was a statistically significant decline in the CD4 level in our study, the absolute decline was small given the high CD4 level overall among the participants, the CD8 level declined as well and there was no significant change in the CD4/CD8 ratio. The absolute magnitude of these declines is therefore unlikely to have clinical significance in our three cohorts.

Limited clinical activity has been shown for therapeutic vaccines against HPV in some studies. SGN-00101 had activity against genital warts [13] and Zyc101a induced statistically significant regression of CIN in women under the age of 25 years but not in older women [14]. As in these earlier studies, clinical response in our study did not correlate with having HPV16, suggesting the possibility of cross-protection among HPV types. This Phase I/II study was not powered to detect the true disease response rate or optimal dose. Nevertheless, our data suggest that SGN-00101 has clinical activity, with a PR or CR observed in one-third of participants. The significance of a PR is not clear, but it was notable that two of four participants with a PR became HPV DNA negative, as did the one participant with a CR. In contrast, none of 10 participants with no clinical response showed clearance of HPV DNA. These data suggest that a PR represents a true biological response. Additional follow-up would be needed to determine if these AIN 1 lesions were in the process of regressing completely or if they would revert to HG-AIN. Further, it is not certain whether the regression rate observed in this study differs from the natural history of HG-AIN, but CR is rare [15] as is clearance of anal HPV infection.

This study showed that the 1000/μg dose can be administered safely in HIV-positive individuals. While there were no data to suggest a dose effect of the drug, the one CR was in the 1000/μg cohort and we recommend that future studies be performed using this dose. Our data should be interpreted with caution because our sample size was small and there was no control group. The participants were selected to have a relatively high CD4 cell count and low HIV VL and therefore may not be generalizeable to all HIV-positive individuals. However, they support further studies of SGN-00101 to treat HG-AIN in HIV-positive individuals in larger Phase II and Phase III trials.

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