Long-term open-label vebicorvir for chronic HBV infection: Safety and off-treatment responses

Background & Aims

The investigational first-generation core inhibitor vebicorvir (VBR) demonstrated safety and antiviral activity over 24 weeks in two phase IIa studies in patients with chronic HBV infection. In this long-term extension study, patients received open-label VBR with nucleos(t)ide reverse transcriptase inhibitors (NrtIs).

Methods

Patients in this study (NCT03780543) previously received VBR + NrtI or placebo + NrtI in parent studies 201 (NCT03576066) or 202 (NCT03577171). After receiving VBR + NrtI for ≥52 weeks, stopping criteria (based on the treatment history and hepatitis B e antigen status in the parent studies) were applied, and patients either discontinued both VBR + NrtI, discontinued VBR only, or continued both VBR + NrtI. The primary efficacy endpoint was the proportion of patients with HBV DNA <20 IU/ml at 24 weeks off treatment.

Results

Ninety-two patients entered the extension study and received VBR + NrtI. Long-term VBR + NrtI treatment led to continued suppression of HBV nucleic acids and, to a lesser extent, HBV antigens. Forty-three patients met criteria to discontinue VBR + NrtI, with no patients achieving the primary endpoint; the majority of virologic rebound occurred ≥4 weeks off treatment. Treatment was generally well tolerated, with few discontinuations due to adverse events (AEs). There were no deaths. Most AEs and laboratory abnormalities were related to elevations in alanine aminotransferase and occurred during the off-treatment or NrtI-restart phases. No drug-drug interactions between VBR + NrtI and no cases of treatment-emergent resistance among patients who adhered to treatment were observed.

Conclusions

Long-term VBR + NrtI was safe and resulted in continued reductions in HBV nucleic acids following completion of the 24-week parent studies. Following treatment discontinuation, virologic relapse was observed in all patients. This first-generation core inhibitor administered with NrtI for at least 52 weeks was not sufficient for HBV cure.

Clinical trial number

NCT03780543.

Impact and implications

Approved treatments for chronic hepatitis B virus infection (cHBV) suppress viral replication, but viral rebound is almost always observed after treatment discontinuation, highlighting an unmet need for improved therapies with finite treatment duration producing greater therapeutic responses that can be sustained off treatment. First-generation core inhibitors, such as vebicorvir, have mechanisms of action orthogonal to standard-of-care therapies that deeply suppress HBV viral replication during treatment; however, to date, durable virologic responses have not been observed after treatment discontinuation. The results reported here will help researchers with the design and interpretation of future studies investigating core inhibitors as possible components of finite treatment regimens for patients with cHBV. It is possible that next-generation core inhibitors with enhanced potency may produce deeper and more durable antiviral activity than first-generation agents, including vebicorvir.

Safety, pharmacokinetics and antiviral activity of ABI-H2158, a hepatitis B virus core inhibitor: A randomized, placebo-controlled phase 1 study

Treatment for chronic hepatitis B virus infection (cHBV) is mostly indefinite, with new finite-duration therapies needed. We report safety, pharmacokinetics and antiviral activity of the investigational HBV core inhibitor ABI-H2158. This Phase 1a/b study (NCT03714152) had three parts: Part A, participants received a single ascending oral dose of ABI-H2158 (5-500 mg) or placebo; Part B, participants received multiple doses of ABI-H2158 300 mg once (QD) or twice (BID) daily or placebo, for 10 days; Part C, cHBV patients received ABI-H2158 (100, 300, or 500 mg QD or 300 mg BID) or placebo, for 14 days. Ninety-three participants enrolled. In Parts A/B, there were no serious adverse events (SAEs) or deaths, and all treatment-emergent AEs (TEAEs) were Grade 1. In Part C, two patients had Grade 3 TEAEs unrelated to ABI-H2158; there were no deaths, SAEs or Grade 4 TEAEs. In Part A, median time to maximum ABI-H2158 plasma concentration (T_max ) and mean terminal elimination half-life (t_½ ) were 1-4 and 9.8-20.7 h, and area under the plasma concentration-time curve increased dose proportionally. In Part B, Day 10 T_max was 2 h, mean t_½ was 15.5-18.4 h, and exposure accumulated 1.7- to 3.1-fold. In Part C, Day 14 T_max was 1 h, exposure accumulated 1.4- to 1.8-fold, and ABI-H2158 was associated with >2 log₁₀ declines in HBV nucleic acids. In conclusion, ABI-H2158 in cHBV patients following 14 days of dosing was well tolerated and demonstrated potent antiviral activity. Safety and pharmacokinetics supported future QD dosing.

Safety and efficacy of vebicorvir in virologically suppressed patients with chronic hepatitis B virus infection

BACKGROUND & AIMS

HBV nucleos(t)ide reverse transcriptase inhibitors (NrtIs) do not completely suppress HBV replication. Previous reports indicate persistent viremia during NrtI treatment despite HBV DNA being undetectable. HBV core inhibitors may enhance viral suppression when combined with NrtIs. This phase II trial (NCT03576066) evaluated the efficacy and safety of the investigational core inhibitor, vebicorvir (VBR), in virologically- suppressed patients on NrtIs.

METHODS

Non-cirrhotic, NrtI-suppressed patients with chronic HBV were randomised to VBR 300 mg once daily or matching placebo (PBO) for 24 weeks. Treatment was stratified by hepatitis B e antigen (HBeAg) status. The primary endpoint was change from Baseline in serum HBeAg or hepatitis B surface antigen (HBsAg) after 24 weeks.

RESULTS

Of 73 patients enrolled, 47 were HBeAg positive and 26 were HBeAg negative. In HBeAg-positive and -negative patients, there were no differences in the change from Baseline at Week 24 for HBsAg or HBeAg. Using a novel, high-sensitivity assay to detect HBV DNA, a greater proportion of patients with detectable HBV DNA at Baseline achieved undetectable HBV DNA at Week 24 in the VBR+NrtI vs. PBO+NrtI group. In HBeAg-positive patients, a greater change from Baseline in HBV pregenomic (pg)RNA was observed at Week 24 with VBR+NrtI vs. PBO+NrtI. Treatment-emergent adverse events (TEAEs) in VBR+NrtI patients included upper respiratory tract infection, nausea, and pruritus. No serious adverse events, Grade 4 TEAEs, or deaths were reported.

CONCLUSIONS

In this 24-week study, VBR+NrtI demonstrated a favourable safety and tolerability profile. While there were no significant changes in viral antigen levels, enhanced viral suppression was demonstrated by greater changes in DNA and pgRNA with the addition of VBR compared to NrtI alone.

CLINICAL TRIALS NUMBER

NCT03576066.

LAY SUMMARY

Core inhibitors represent a novel approach for the treatment of chronic hepatitis B virus (HBV) infection, with mechanisms of action distinct from existing treatments. In this study, vebicorvir added to existing therapy reduced HBV replication to a greater extent than existing treatment and was generally safe and well tolerated.

Sofosbuvir plus ribavirin with or without peginterferon for the treatment of hepatitis C virus: Results from a phase 3b study in China

BACKGROUND AND AIM

Sofosbuvir is a nucleotide analog inhibitor of the hepatitis C virus (HCV) NS5B RNA polymerase with pangenotypic potency. This phase 3b study evaluated the safety and efficacy of sofosbuvir + ribavirin ± peginterferon in Chinese patients infected with HCV genotype 1, 2, 3, or 6.

METHODS

Patients with genotype 1 or 6 received sofosbuvir + peginterferon/ribavirin for 12 weeks or sofosbuvir + ribavirin for 24 weeks, depending on prior treatment and interferon eligibility. Patients with genotype 2 or 3 received sofosbuvir + ribavirin for 12 or 24 weeks, respectively. The primary endpoint was sustained virologic response at 12 weeks after the end of treatment (SVR12).

RESULTS

Of 389 patients, 42% had genotype 1, 16% genotype 2, 32% genotype 3, and 9% genotype 6. Half were male, 58% were treatment-naïve, and 15% had cirrhosis. SVR12 rates for patients receiving 12 weeks of sofosbuvir + peginterferon/ribavirin were 94% (95% confidence interval [CI], 87-98%) for HCV genotype 1 and 97% (95% CI, 84-100%) for genotype 6. SVR12 rates for those receiving sofosbuvir + ribavirin for 24 weeks were 95% (95% CI, 87-99%) for genotype 1, 100% (95% CI, 40-100%) for genotype 6, and 95% (95% CI, 90-98%) for genotype 3. For genotype 2 patients receiving sofosbuvir + ribavirin for 12 weeks, the SVR12 rate was 92% (95% CI, 83-97%). Twenty patients (5%) relapsed. Ten (3%) experienced serious adverse events. Three (< 1%) discontinued treatment because of adverse events, of whom one died because of treatment-unrelated adverse events.

CONCLUSIONS

Sofosbuvir-based regimens were highly effective and safe in Chinese patients with HCV genotype 1, 2, 3, or 6, suggesting sofosbuvir could serve as the backbone for HCV treatment in China irrespective of genotype.

Efficacy of Ledipasvir and Sofosbuvir Treatment of HCV Infection in Patients Coinfected With HBV

BACKGROUND & AIMS

There have been reports of reactivation of hepatitis B virus (HBV) infection during treatment of hepatitis C virus (HCV) infection with direct-acting antiviral agents. We performed a prospective study of risks and outcomes of HCV infection treatment with ledipasvir and sofosbuvir in patients with HBV infection.

METHODS

We performed a phase 3b, multicenter, open-label study in Taiwan of 111 patients with HCV infection (61% HCV genotype 1, 39% HCV genotype 2 infection; 62% women, 16% with compensated cirrhosis) along with HBV infection. All but 1 were positive for the hepatitis B surface antigen (HBsAg); 1 patient who was HBsAg-positive at screening was found to be HBsAg-negative at baseline. Overall, 33% of participants had received prior treatment for HCV and 5% had previously been treated for HBV; no patient was on HBV therapy at the start of the study. All patients received a fixed-dose combination of 90 mg of the HCV NS5A inhibitor ledipasvir with 400 mg of the NS5B nucleotide analogue inhibitor sofosbuvir, once daily for 12 weeks. The primary endpoint was sustained virologic response 12 weeks after the end of therapy.

RESULTS

All 111 patients (100%) achieved a sustained virologic response. Of the 37 patients with baseline HBV DNA below 20 IU/mL, 31 (84%) had at least 1 episode of quantifiable HBV DNA through posttreatment week 12. Of the 74 patients with baseline HBV DNA levels of 20 IU/mL or more, 39 (53%) had increases of HBV DNA greater than 1 log₁₀ IU/mL through posttreatment week 12. Overall, 5 patients had increased levels of HBV DNA concomitant with a level of alanine aminotransferase >2 times the upper limit of normal through posttreatment week 12. Of these, 3 patients started HBV treatment. In addition, 1 patient with HBV reactivation since week 8 and concomitant alanine aminotransferase elevation >2 times upper limit of normal at posttreatment week 48 started treatment at posttreatment week 53. This patient had clinical signs and symptoms associated with HBV reactivation. The most common adverse events were headache, upper respiratory infection, and fatigue.

CONCLUSIONS

In a prospective study, the combination of ledipasvir and sofosbuvir for 12 weeks produced a sustained virologic response in 100% of patients with HCV infection who were coinfected with HBV. Most patients had an increase in level of HBV DNA not associated with signs or symptoms. ClinicalTrials.gov no: NCT02613871.

Efficacy of sofosbuvir plus ribavirin in treatment-naive patients with genotype-1 and -3 HCV infection: results from a Russian Phase IIIb study

BACKGROUND

In this Phase IIIb study, we evaluated the efficacy and safety of the oral nucleotide analogue inhibitor sofosbuvir plus ribavirin, with special attention given to viral resistance, in Russian patients with HCV genotype-1 or -3.

METHODS

Treatment-naive patients with and without compensated cirrhosis were randomized (1:1) to receive 16 or 24 weeks of once-daily sofosbuvir 400 mg plus twice-daily oral ribavirin 1,000 or 1,200 mg/day. The primary efficacy end point was the proportion of patients with sustained viral response 12 weeks after the end of treatment (SVR12). Viral resistance testing was performed by deep sequencing on all baseline samples and for patients who experienced virological failure.

RESULTS

SVR12 rates for patients with genotype-1 HCV were 50% and 76% for those in the 16-week and 24-week groups, respectively, and for patients with genotype-3 HCV, SVR12 rates were 87% and 90% for patients in the 16-week and 24-weeks groups, respectively. Genotype-1 patients with the L159F resistance-associated variant who received 16 weeks of treatment had lower SVR12 rates than those without, but in patients who received 24 weeks of treatment, response rates were similar in those with and without L159F (80% versus 74%). Sofosbuvir plus ribavirin was well tolerated with no deaths, adverse event-related study drug discontinuations, or grade 3 or 4 adverse events, and few grade 3 or 4 laboratory abnormalities.

CONCLUSIONS

Sofosbuvir plus ribavirin for 16 or 24 weeks was associated with a high SVR rate in patients with HCV genotype-3. Among HCV genotype-1b patients, the presence of the L159F variant at baseline was associated with a lower SVR rate in those treated for 16 weeks but not in those treated for 24 weeks. Sofosbuvir plus ribavirin was safe and well tolerated regardless of treatment duration. Clinicaltrials.gov number NCT01896193.

Chronic hepatitis C virus infection in India: Regional demographics and distribution of viral genotypes

BACKGROUND AND AIMS

Although chronic hepatitis C virus (HCV) infection affects millions of people in India, few studies have assessed host, viral, and disease characteristics of chronically infected patients at national and regional levels. Such information is critical to support large scale screening and treatment initiatives for chronic HCV infection in India.

METHODS

Patients with known chronic HCV infection making routine or for-cause visits to the participating study centers were enrolled in this observational study. Patients attended a single outpatient visit during which demographics and medical history were collected, a physical examination was performed, and blood and urine samples were collected for laboratory assessments. Samples were analyzed to determine HCV genotypes and subtypes, and genotypes of interferon lambda 3 (IFNL3) single nucleotide polymorphism. No therapeutic interventions were administered.

RESULTS

We enrolled 500 patients at 19 centers, categorized into four geographic regions (North, South, East, and West). All patients self-identified as Indian, and most (66 %) were male. Genotype 3 was the most common genotype overall (54 %); however, its prevalence varied greatly by region, ranging from 34 % in the South to 69 % in the East. Genotypes 1 (24 %) and 4 (6 %) were the next most common, and HCV genotype could not be determined for 16 % of patients.

CONCLUSIONS

This prospective survey suggests that demographics, viral, and host factors in patients with chronic HCV infection are highly variable in India and pose significant challenges for the implementation of broad-scale screening and treatment initiatives.

Ledipasvir plus sofosbuvir for 12 weeks in patients with hepatitis C genotype 4 infection

Genotype 4 hepatitis C virus (HCV) was considered difficult to treat in the era of pegylated interferon-alpha (Peg-IFN-α) and ribavirin regimens. We evaluated the efficacy and safety of therapy with the nonstructural (NS) 5A inhibitor, ledipasvir, combined with the NS5B polymerase inhibitor, sofosbuvir, in patients with HCV genotype 4. In this phase 2, open-label study, 44 patients (22 treatment naïve and 22 treatment experienced) received a fixed-dose combination tablet of 90 mg of ledipasvir and 400 mg of sofosbuvir orally once-daily for 12 weeks. The primary endpoint was the percentage of patients with HCV RNA <15 IU/mL 12 weeks after stopping therapy (SVR12). Among study participants, HCV genotype 4 subtypes were well represented (4a, n = 25; 4d, n = 10; other subtypes, n = 9). Ten patients (23%) had compensated cirrhosis. Of the 22 treatment-experienced patients, 21 (95%) had a non-CC IL-28B genotype. All 44 patients completed the full 12 weeks of dosing. The SVR12 rate was 93% (41 of 44; 95% confidence interval, 81-99). SVR12 rates were similar between treatment-naïve (95%; 21 of 22) and treatment-experienced (91%; 20 of 22) patients. All 3 patients who did not achieve SVR12 had virological relapse within 4 weeks of the end of treatment; all 3 had baseline HCV RNA ≥800,000 IU/mL, a non-CC IL-28B genotype, and pretreatment NS5A resistance-associated variants. None of the patients who relapsed had cirrhosis. The most common adverse events were asthenia, headache, and fatigue. No patients experienced a serious adverse event.

CONCLUSION

The all-oral regimen of ledipasvir and sofosbuvir is an effective and safe treatment for a wide range of HCV 4 subtypes in both treatment-naïve and -experienced patients, including those with compensated cirrhosis. (EudraCT number: 2013-003978-27; Clinicaltrials.gov NCT02081079) (Hepatology 2016;64:1049-1056).

A phase 3b study of sofosbuvir plus ribavirin in Taiwanese patients with chronic genotype 2 hepatitis C virus infection

BACKGROUND & AIMS

In Taiwan, patients with chronic hepatitis C virus (HCV) infection are currently treated with pegylated interferon-alpha plus ribavirin, but interferon-based regimens can be poorly tolerated, especially by those with advanced liver disease and the elderly. Sofosbuvir, an oral nucleotide analogue inhibitor of HCV NS5B polymerase, is approved in Europe, the USA and Japan for treating chronic HCV infection. This phase 3b study examined the efficacy and safety of sofosbuvir plus ribavirin in Taiwanese patients with chronic genotype 2 HCV infection ± compensated cirrhosis.

METHODS

In this multicentre, open-label, phase 3b (NCT02021643) study, 87 patients (n = 43, treatment-naive; n = 44, treatment-experienced) received 12 weeks of treatment with sofosbuvir plus weight-based ribavirin. The primary efficacy endpoint was the proportion of patients with sustained virological response 12 weeks after treatment discontinuation (SVR12). Safety and pharmacokinetic data were also collected.

RESULTS

All 87 patients (100%; 95% confidence interval, 92-100%) achieved SVR12, including the 13 patients with compensated cirrhosis. The most common treatment-emergent adverse events (AEs) were insomnia (16%, 14/87) and upper respiratory tract infection (16%, 14/87). No grade 3 or grade 4 AE was reported. There was one serious AE (biliary colic), which was deemed unrelated to study treatment. Laboratory abnormalities other than ribavirin-related reductions in haemoglobin were uncommon.

CONCLUSIONS

The results from this phase 3b study demonstrate that 12 weeks of treatment with the interferon-free regimen sofosbuvir plus ribavirin is effective and well tolerated in both treatment-naive and treatment-experienced Taiwanese patients with chronic genotype 2 HCV infection.

Ledipasvir/sofosbuvir fixed-dose combination tablet in Taiwanese patients with chronic genotype 1 hepatitis C virus

BACKGROUND AND AIM

Pegylated-interferon-alpha plus ribavirin is the current standard-of-care regimen for treating chronic hepatitis C virus (HCV) infection in Taiwan; however, interferon-based regimens can be poorly tolerated. The interferon-free, two-drug, fixed-dose combination tablet ledipasvir/sofosbuvir is approved in Europe, the USA, and Japan for treating chronic genotype 1 HCV infection. Little is known about its efficacy/safety in Taiwanese patients.

METHODS

In this multicenter, open-label, phase 3b (NCT02021656) study, 85 Taiwanese patients (n = 42, treatment-naïve; n = 43, treatment-experienced) with chronic genotype 1 HCV infection (±compensated cirrhosis) received 12 weeks of ledipasvir/sofosbuvir fixed-dose combination tablet. The primary efficacy end point was the proportion of patients with sustained virologic response 12 weeks after treatment discontinuation (SVR12). Safety and pharmacokinetic data were collected.

RESULTS

The overall SVR12 rate was 98% (83/85), with 100% (42/42) and 95% (41/43) of treatment-naïve and treatment-experienced patients, respectively, achieving SVR12. There were no on-treatment virologic failures. One patient relapsed after treatment discontinuation; one patient withdrew consent on day 2. The most common treatment-emergent adverse event (AE) was headache (14%, 12/85). There was one grade 3 AE (small cell lung cancer unrelated to ledipasvir/sofosbuvir), no grade 4 AEs, and four grade 3-4 laboratory abnormalities. Only the patient with small cell lung cancer prematurely discontinued treatment. Two patients reported three serious AEs; none was considered related to ledipasvir/sofosbuvir.

CONCLUSIONS

Data from this phase 3b study suggest that 12 weeks of once-daily treatment with the interferon-free, ribavirin-free regimen ledipasvir/sofosbuvir is effective and well-tolerated in Taiwanese patients with chronic genotype 1 HCV infection, irrespective of treatment history.

A phase IIIb study of ledipasvir/sofosbuvir fixed-dose combination tablet in treatment-naïve and treatment-experienced Korean patients chronically infected with genotype 1 hepatitis C virus

BACKGROUND

The standard-of-care regimen for chronic hepatitis C virus (HCV) infection in Korea, pegylated-interferon-alpha plus ribavirin, is poorly tolerated. Ledipasvir/sofosbuvir is a two-drug, fixed-dose combination tablet approved in the USA, European Union, and Japan for chronic genotype 1 HCV infection.

METHODS

This single-arm, phase IIIb study (NCT02021656) investigated the efficacy and safety of ledipasvir/sofosbuvir fixed-dose combination tablet for 12 weeks in treatment-naïve and treatment-experienced Korean patients chronically infected with genotype 1 HCV with or without compensated cirrhosis.

RESULTS

The proportion of patients with sustained virologic response 12 weeks after treatment discontinuation (SVR12) was 99 % (92/93), with rates of 100 % (46/46) and 98 % (46/47) in treatment-naïve and treatment-experienced patients, respectively. There were no on-treatment failures. One patient relapsed after the end of treatment. The most common treatment-emergent adverse events were headache (8 %, 7/93) and fatigue (6 %, 6/93). There were no grade 3 or 4 adverse events, seven grade 3 laboratory abnormalities, and one premature discontinuation of study treatment (due to nonserious mouth ulceration). None of the three reported serious adverse events were related to treatment.

CONCLUSIONS

These data suggest that 12 weeks of ledipasvir/sofosbuvir is effective and well tolerated in treatment-naïve and treatment-experienced Korean patients with chronic genotype 1 HCV infection.

Correlates of disease-specific knowledge among patients with chronic hepatitis B or hepatitis C infection in India

BACKGROUND

Patient knowledge about chronic diseases increases health-promoting behaviors and improves clinical outcomes. We assessed this association for patients with chronic viral hepatitis.

METHODS

Untreated patients chronically infected with HBV (n = 500) or HCV (n = 500) were enrolled at 19 centers across India. A survey, adapted from the US CDC National Health and Nutrition Examination Survey (NHANES) questionnaire, was administered at a single visit to assess HBV/HCV knowledge, community disease awareness, treatment quality, and healthcare barriers. We developed the India Hepatitis Knowledge Index (IHKI), where a higher IHKI score (range 0-10) indicates increased hepatitis knowledge. Multivariate regression models evaluated demographic and disease factors.

RESULTS

The overall mean IHKI score was 5.6 out of 10, with higher scores among patients with HBV (5.9) than HCV (5.3); p < 0.001. In HBV patients lower IHKI was associated with shorter disease duration, government clinic attendance (p < 0.0001), fewer personal experiences with HBV (p < 0.0001), and residing in northern India. Among HCV patients, lower IHKI was associated with shorter disease duration, community (p < 0.0001) and government clinic attendance (p < 0.0001), and fewer personal experiences with HCV (p < 0.0001). Among HBV patients, IHKI was independently associated with disease severity as assessed by MELD score, albumin, and APRI. This association was strongest for HBV patients with elevated ALT and HBV DNA >2000 IU/ml. Among HCV patients, IHKI results had no significant associations with disease severity.

CONCLUSIONS

The association of IHKI with disease underscores the need to understand connections between hepatitis knowledge and progression and may guide efforts to address patient education and awareness of chronic viral hepatitis in India.

A phase 3b study of sofosbuvir plus ribavirin in treatment-naive and treatment-experienced Korean patients chronically infected with genotype 2 hepatitis C virus

In Korea, patients with chronic hepatitis C virus (HCV) infection are typically treated with pegylated interferon-alpha plus ribavirin, but interferons are contraindicated in many patients and are often poorly tolerated, particularly by the elderly and those with advanced liver disease. No interferon-free treatment regimens are approved in Korea. Sofosbuvir is an oral nucleotide analog inhibitor of the HCV nonstructural 5B RNA polymerase. It is approved in the USA, European Union and Japan for treating a number of HCV genotypes, including genotype 2. Genotype 2 has a seroprevalence of 38-46% in Korea. This single-arm, phase 3b study (NCT02021643) examined the efficacy and safety of sofosbuvir plus ribavirin (12-week duration) in chronic genotype 2 HCV-infected treatment-naive and treatment-experienced Korean patients with and without cirrhosis. The proportion of patients with sustained virologic response 12 weeks after treatment discontinuation (SVR12) was 97% (125/129), with 96% (101/105) of treatment-naive and 100% (24/24) of treatment-experienced patients achieving SVR12. Two patients experienced virologic failure (n = 1, on-treatment failure; n = 1, relapse). No patient discontinued study treatment due to an adverse event (AE). The most common treatment-emergent AEs were headache (18%, 23/129) and pruritus (15%, 19/129). Few patients had grade 3 AEs (5%, 6/129) or grade 3 laboratory abnormalities (12%, 15/129). No grade 4 AE was reported. These data suggest that 12 weeks of treatment with the all-oral, interferon-free regimen of sofosbuvir plus ribavirin is effective and well tolerated in Korean patients with chronic genotype 2 HCV infection.

Safety and efficacy of ledipasvir/sofosbuvir for the treatment of genotype 1 hepatitis C in subjects aged 65 years or older

Elderly subjects have been historically underrepresented in clinical trials involving antiviral hepatitis C therapies. The aim of this analysis was to retrospectively evaluate the safety and efficacy of ledipasvir/sofosbuvir (LDV/SOF) by age groups of <65 years versus ≥65 years among subjects enrolled in phase 3 trials. Four open-label phase 3 clinical trials evaluated the safety and efficacy of LDV/SOF with or without ribavirin (RBV) for the treatment of genotype 1 chronic hepatitis C virus. Sustained virological response at 12 weeks, treatment-emergent adverse events (AEs), and graded laboratory abnormalities were analyzed according to age group. Of the 2293 subjects enrolled in four phase 3 trials, 264 (12%) were ≥65 years of age, of whom 24 were aged ≥75 years. Sustained virological response at 12 weeks was achieved by 97% (1965/2029) of subjects aged <65 years and 98% (258/264) of subjects aged ≥65 years. The most common AEs in both LDV/SOF groups that occurred in ≥10% of subjects were headache and fatigue. The rate of study discontinuation due to AEs was similar in the two age cohorts. The use of RBV in 1042 (45%) subjects increased the number of AEs, treatment-related AEs, and AEs leading to study drug modification/interruption, particularly among elderly subjects.

CONCLUSIONS

LDV/SOF with or without RBV was highly effective for treatment of genotype 1 chronic hepatitis C virusin subjects aged 65 and older. Addition of RBV did not increase sustained virological response at 12 weeks rates but led to higher rates of AEs, especially in elderly subjects.

Sofosbuvir plus ribavirin for the treatment of patients with chronic genotype 1 or 6 hepatitis C virus infection in Hong Kong

BACKGROUND

In Hong Kong, most patients with hepatitis C virus (HCV) have either genotype 6a or 1b infection.

AIM

To evaluate the efficacy and safety of sofosbuvir with ribavirin in treatment-naïve patients in Hong Kong with HCV genotype 1 or 6.

METHODS

In an open-label study, patients were randomised to sofosbuvir 400 mg once daily plus ribavirin 1000-1200 divided twice daily for 12 (n = 10), 16 (n = 11) or 24 (n = 10) weeks. The primary endpoint was the percentage of patients with HCV RNA < LLOQ (lower limit of quantification, 25 IU/mL) 12 weeks after cessation of therapy (SVR12).

RESULTS

All 31 patients (20 HCV genotype 1 and 11 genotype 6) had HCV RNA < LLOQ by Week 4 of treatment and at their last on-treatment visit. SVR12 rates were high in all treatment groups: 100% (10/10) for 12 weeks, 100% (11/11) for 16 weeks and 90% (9/10) for 24 weeks of therapy. The only patient who did not reach SVR12 had genotype 1 HCV and relapsed at post-treatment Week 4. Sofosbuvir with ribavirin was generally well tolerated. The most common adverse events were malaise (13%) and upper respiratory tract infection (13%), followed by anaemia (10%). No patients experienced serious adverse events. One patient discontinued treatment at Week 16 because of an adverse event. The event, upper respiratory tract infection, was not considered treatment related by the investigator. This subject achieved SVR12.

CONCLUSIONS

The all-oral regimen sofosbuvir plus ribavirin is effective in treatment-naïve patients in Hong Kong with genotype 1 or 6 HCV.

TRIAL REGISTRATION NUMBER

NCT02021643.

Sofosbuvir plus ribavirin for treating Egyptian patients with hepatitis C genotype 4

BACKGROUND & AIMS

Egypt has the highest prevalence of chronic hepatitis C virus (HCV) infection in the world, and more than 90% of patients are infected with genotype 4 virus. We evaluated the efficacy and safety of the HCV polymerase inhibitor sofosbuvir in combination with ribavirin in HCV genotype 4 patients in Egypt.

METHODS

Treatment-naïve or treatment-experienced patients with genotype 4 HCV infection (n=103) were randomly assigned to receive either 12 or 24 weeks of sofosbuvir 400 mg and ribavirin 1000-1200 mg daily. Randomization was stratified by prior treatment experience and by presence or absence of cirrhosis. The primary endpoint was the percentage of patients with HCV RNA <25 IU/ml 12 weeks after therapy (SVR12).

RESULTS

Among all patients, 52% had received prior HCV treatment and 17% had cirrhosis at baseline. SVR12 rates were 90% (46/51) with 24 weeks and 77% (40/52) with 12 weeks of sofosbuvir and ribavirin therapy. Patients with cirrhosis at baseline had lower rates of SVR12 (63% 12 weeks, 78% 24 weeks) than those without cirrhosis (80% 12 weeks, 93% 24 weeks). The most common adverse events were fatigue, headache, insomnia, and anemia. Two patients experienced serious adverse events (cerebral ischemia, dyspnea). No adverse events resulted in treatment discontinuation.

CONCLUSION

Sofosbuvir plus ribavirin for 12 or 24 weeks is effective in treating both treatment-naïve and treatment-experienced Egyptian patients with genotype 4 HCV.

Elevated Intracranial Pressure and Cerebral Edema following Permanent MCA Occlusion in an Ovine Model

INTRODUCTION

Malignant middle cerebral artery (MCA) stroke has a disproportionately high mortality due to the rapid development of refractory space-occupying cerebral edema. Animal models are essential in developing successful anti-edema therapies; however to date poor clinical translation has been associated with the predominately used rodent models. As such, large animal gyrencephalic models of stroke are urgently needed. The aim of the study was to characterize the intracranial pressure (ICP) response to MCA occlusion in our recently developed ovine stroke model.

MATERIALS AND METHODS

30 adult female Merino sheep (n = 8-12/gp) were randomized to sham surgery, temporary or permanent proximal MCA occlusion. ICP and brain tissue oxygen were monitored for 24 hours under general anesthesia. MRI, infarct volume with triphenyltetrazolium chloride (TTC) staining and histology were performed.

RESULTS

No increase in ICP, radiological evidence of ischemia within the MCA territory but without space-occupying edema, and TTC infarct volumes of 7.9+/-5.1% were seen with temporary MCAO. Permanent MCAO resulted in significantly elevated ICP, accompanied by 30% mortality, radiological evidence of space-occupying cerebral edema and TTC infarct volumes of 27.4+/-6.4%.

CONCLUSIONS

Permanent proximal MCAO in the sheep results in space-occupying cerebral edema, raised ICP and mortality similar to human malignant MCA stroke. This animal model may prove useful for pre-clinical testing of anti-edema therapies that have shown promise in rodent studies.

Sofosbuvir plus ribavirin for the treatment of chronic genotype 4 hepatitis C virus infection in patients of Egyptian ancestry

BACKGROUND & AIMS

We conducted an open-label phase 2 study to assess the efficacy and safety of the oral nucleotide polymerase inhibitor sofosbuvir in combination with ribavirin in patients of Egyptian ancestry, chronically infected with genotype 4 hepatitis C virus (HCV).

METHODS

Treatment-naive and previously treated patients with genotype 4 HCV were randomly allocated in a 1:1 ratio to receive sofosbuvir 400mg and weight-based ribavirin, for 12 or 24 weeks. The primary efficacy endpoint was the proportion of patients with sustained virologic response (HCV RNA <25IU/ml) 12 weeks after cessation of therapy (SVR12).

RESULTS

Thirty treatment-naive and thirty previously treated patients were enrolled and treated for 12 weeks (n=31) or 24 weeks (n=29). Overall, 23% of patients had cirrhosis and 38% had diabetes. 14% of treatment-naive patients were interferon ineligible and 63% of treatment-experienced patients had prior non-response. SVR12 was achieved by 68% of patients (95% CI, 49-83%) in the 12-week group, and by 93% of patients (95% CI, 77-99%) in the 24-week group. The most common adverse events were headache, insomnia, and fatigue. No patient discontinued treatment due to an adverse event.

CONCLUSIONS

The findings from the present study suggest that 24 weeks of sofosbuvir plus ribavirin is an efficacious and well tolerated treatment in patients with HCV genotype 4 infection.

Ledipasvir and sofosbuvir fixed-dose combination with and without ribavirin for 12 weeks in treatment-naive and previously treated Japanese patients with genotype 1 hepatitis C: an open-label, randomised, phase 3 trial

BACKGROUND

Compared with other countries, patients with chronic hepatitis C infection in Japan tend to be older, have more advanced liver disease, and are more likely to have been previously treated for hepatitis C. We aimed to assess the efficacy and safety of an all-oral, fixed-dose combination of the hepatitis C virus NS5A inhibitor ledipasvir and the NS5B nucleotide polymerase inhibitor sofosbuvir with and without ribavirin for 12 weeks in treatment-naive and previously treated Japanese patients with chronic genotype 1 hepatitis C virus infection.

METHODS

In this randomised, open-label study, we enrolled patients from 19 clinical Japanese centres. Patients were randomly assigned (1:1) to receive either ledipasvir (90 mg) and sofosbuvir (400 mg) or ledipasvir, sofosbuvir, and ribavirin (dosed according to the Japanese Copegus product label-ie, patients ≤60 kg received 600 mg daily, patients >60 kg to ≤80 kg received 800 mg daily, and patients >80 kg received 1000 mg daily) orally once daily for 12 weeks. After completion or early discontinuation of treatment, patients were followed up off-treatment for 24 weeks. Eligible patients were at least 20 years of age with chronic genotype 1 hepatitis C virus infection with serum hepatitis C virus RNA concentrations of at least 5 log10 IU/mL, creatinine clearance of at least 1·0 mL/s, and a platelet count of at least 50 × 10(9) per L. An interactive web response system was used to manage patient randomisation and treatment assignment. Randomisation was stratified by the presence or absence of cirrhosis for treatment-naive patients and stratified by presence or absence of cirrhosis and by previous treatment category (relapser or breakthrough, non-responder, or interferon-intolerant) for previously treated patients. Within each strata, patients were sequentially assigned to either treatment with ledipasvir-sofosbuvir or ledipasvir-sofosbuvir plus ribavirin in a 1:1 ratio with block size of 4. The primary endpoint was sustained virological response 12 weeks after completion of treatment (SVR12) assessed in all patients who were randomly assigned and received at least one dose of study drug; safety outcomes were assessed in all patients who received at least one dose of study drug. This trial is registered with ClinicalTrials.gov, number NCT01975675.

FINDINGS

Between Oct 15, 2013 and Dec 13, 2013, 341 patients were randomly assigned to treatment groups and received at least one dose of study treatment. SVR12 was achieved in all 171 (100%) patients (83 of 83 treatment naive and 88 of 88 treatment experienced) receiving ledipasvir-sofosbuvir (95% CI 98-100) and 167 (98%) of 170 patients (80 of 83 treatment naive and 87 of 87 treatment experienced) receiving ledipasvir-sofosbuvir plus ribavirin (95% CI 95-100). Of the 76 patients with baseline NS5A resistant variants, 75 (99%) achieved SVR12. Two (1·2%) of 170 patients in the ledipasvir-sofosbuvir plus ribavirin group discontinued treatment because of adverse events. The most common adverse events were nasopharyngitis (50 [29·2%] of 171), headache (12 [7·0%] of 171), and malaise (nine [5·3%] of 171) in patients receiving ledipasvir-sofosbuvir; and nasopharyngitis (40 [23·5%] of 170), anaemia (23 [13·5%] of 170), and headache in those receiving ledipasvir-sofosbuvir and ribavirin (15 [8·8%] of 170).

INTERPRETATION

Although existing regimens for the treatment of hepatitis C virus are effective for many patients, medical needs remain unmet, particularly in Japan where the population with hepatitis C virus genotype 1 is generally older and treatment-experienced, with advanced liver disease. The efficacy, tolerability, and absence of drug-drug interactions of ledipasvir-sofosbuvir suggest that it could be an important option for treatment of genotype 1 hepatitis C virus in Japanese patients.

FUNDING

Gilead Sciences.

A surgical model of permanent and transient middle cerebral artery stroke in the sheep

Background

Animal models are essential to study the pathophysiological changes associated with focal occlusive stroke and to investigate novel therapies. Currently used rodent models have yielded little clinical success, however large animal models may provide a more suitable alternative to improve clinical translation. We sought to develop a model of acute proximal middle cerebral artery (MCA) ischemic stroke in sheep, including both permanent occlusion and transient occlusion with reperfusion.

Materials and Methods

18 adult male and female Merino sheep were randomly allocated to one of three groups (n = 6/gp): 1) sham surgery; 2) permanent proximal MCA occlusion (MCAO); or 3) temporary MCAO with aneurysm clip. All animals had invasive arterial blood pressure, intracranial pressure and brain tissue oxygen monitoring. At 4 h following vessel occlusion or sham surgery animals were killed by perfusion fixation. Brains were processed for histopathological examination and infarct area determination. 6 further animals were randomized to either permanent (n = 3) or temporary MCAO (n = 3) and then had magnetic resonance imaging (MRI) at 4 h after MCAO.

Results

Evidence of ischemic injury in an MCA distribution was seen in all stroke animals. The ischemic lesion area was significantly larger after permanent (28.8%) compared with temporary MCAO (14.6%). Sham animals demonstrated no evidence of ischemic injury. There was a significant reduction in brain tissue oxygen partial pressure after permanent vessel occlusion between 30 and 210 mins after MCAO. MRI at 4 h demonstrated complete proximal MCA occlusion in the permanent MCAO animals with a diffusion deficit involving the whole right MCA territory, whereas temporary MCAO animals demonstrated MRA evidence of flow within the right MCA and smaller predominantly cortical diffusion deficits.

Conclusions

Proximal MCAO can be achieved in an ovine model of stroke via a surgical approach. Permanent occlusion creates larger infarct volumes, however aneurysm clip application allows for reperfusion.

Tumor-selective killing by selenite in patient-matched pairs of normal and malignant prostate cells

BACKGROUND

Selenium compounds have been shown to induce apoptosis in a variety of human prostate cancer cell lines. However, the effects of selenium have yet to be examined in normal and malignant cells derived from the same individual. Selenite metabolism consumes glutathione (GSH) and produces superoxide. The generation of reactive oxygen species is an important mechanism in selenite-induced apoptosis.

METHODS

Three patient-matched pairs of primary prostatic epithelial cell cultures from normal and cancer were evaluated for their response to selenite. Apoptosis was measured and the differential response of normal and cancer cells was correlated with the expression of bcl-2, bax, GSH, and manganese superoxide dismutase (MnSOD).

RESULTS

The cancer-derived cells were significantly more sensitive to selenite-induced apoptosis than the corresponding normal cells. Tumor-selective killing was not observed in cells treated with selenomethionine. The ratio of bcl-2:bax was decreased in the cancer-derived cells treated with selenite. Total GSH concentrations were similar in paired normal and cancer cells. Therefore, differences in GSH content do not appear to play a role in tumor-selective killing by selenite. Superoxide is a by-product of selenite metabolism and normal cells showed increased MnSOD expression and SOD activity compared to the cancer-derived cells. Prostate cancer cells treated with the MnSOD mimetic, MnTMPyP, were protected against the cytotoxic effects of selenite.

CONCLUSIONS

Higher MnSOD expression in normal cells may play an important role in eliminating superoxide radicals produced as a result of selenite metabolism and contribute to the tumor-selective killing by selenite in prostate cancer.

The role of radiation-induced apoptosis as a determinant of tumor responses to radiation therapy

Ionizing radiation is an effective means of killing tumor cells. Approximately 50% of all American cancer patients are treated with radiotherapy at some time during the course of their disease, making radiation one of the most widely used cytotoxic therapies. Currently, much effort is focused on understanding the molecular pathways that regulate tumor cell survival following radiotherapy, with the long term goal of developing novel therapeutic strategies for specifically sensitizing tumors to radiation. At present, there is particular interest in the role of tumor cell apoptotic potential as a regulator of both intrinsic and extrinsic determinants of the response of tumors to radiation therapy. Here we review what is currently known about the role of apoptosis as a mechanism of tumor cell killing by ionizing radiation and the relative contribution of apoptosis to cellular radiosensitivity and the ability to control human cancers using radiotherapy. The following topics will be discussed: (1) radiation-induced apoptosis in normal and malignant cells, (2) clinical findings with respect to apoptosis in human cancers treated with radiotherapy, (3) the contribution of apoptosis to intrinsic radiosensitivity in vitro, (4) the relevance of apoptosis to treatment outcome in experimental tumor models in vivo and (5) the potential of exploiting apoptosis as a means to improve the therapeutic efficacy of radiotherapy.

Role of glutathione depletion and reactive oxygen species generation in apoptotic signaling in a human B lymphoma cell line

The primary objective of this study was to determine the sequence of biochemical signaling events that occur after modulation of the cellular redox state in the B cell lymphoma line, PW, with emphasis on the role of mitochondrial signaling. L-Buthionine sulphoximine (BSO), which inhibits gamma glutamyl cysteine synthetase (gammaGCS), was used to modulate the cellular redox status. The sequence and role of mitochondrial events and downstream apoptotic signals and mediators was studied. After BSO treatment, there was an early decline in cellular glutathione (GSH), followed by an increase in reactive oxygen species (ROS) production, which induced a variety of apoptotic signals (detectable at different time points) in the absence of any external apoptotic stimuli. The sequence of biochemical events accompanying apoptosis included a 95% decrease in total GSH and a partial (25%) preservation of mitochondrial GSH, without a significant increase in ROS production at 24h. Early activation and nuclear translocation of the nuclear factor kappa B subunit Rel A was observed at approximately 3h after BSO treatment. Cytochrome c release into the cytosol was also seen after 24h of BSO treatment. p53 protein expression was unchanged after redox modulation for up to 72 h, and p21waf1 independent loss of cellular proliferation was observed. Surprisingly, a truncated form of p53 was expressed in a time-dependent manner, beginning at 24h after BSO incubation. Irreversible commitment to apoptosis occurred between 48 and 72 h after BSO treatment when mitochondrial GSH was depleted, and there was an increase in ROS production. Procaspase 3 protein levels showed a time-dependent reduction following incubation with BSO, notably after 48 h, that corresponded with increasing ROS levels. At 96 h, caspase 3 cleavage products were detectable. The pan-caspase inhibitor zVADfmk, partially blocked the induction of apoptosis at 48 h, and was ineffective after 72 h. PW cells could be rescued from apoptosis by removing them from BSO after up to 48, but not 72 h incubation with BSO. Mitochondrial transmembrane potential (DeltaPsi(m)) remained intact in most of the cells during the 72 h observation period, indicating that DeltaPsi(m) dissipation is not an early signal for the induction of redox dependent apoptosis in PW cells. These data suggest that a decrease in GSH alone can act as a potent early activator of apoptotic signaling. Increased ROS production following mitochondrial GSH depletion, represents a crucial event, which irreversibly commits PW cells to apoptosis.

Rotenone-induced G2/M cell cycle arrest and apoptosis in a human B lymphoma cell line PW

Concentrations of rotenone (ROT) that block electron flow through mitochondrial complex I (100 nM) did not significantly alter either cell viability or the growth of PW cells. However, 10- to 50-fold higher concentrations (1-5 microM) were found to induce a dose-dependent cell cycle arrest predominantly at the G2/M stage of the cycle and apoptosis. Apoptosis was dependent on the cell cycle arrest, since apoptosis but not the G2/M arrest was prevented with the broad spectrum caspase inhibitor zVADfmk. Biochemical features of apoptosis included mitochondrial cytochrome c release, reactive oxygen species generation, and the activation of procaspase 3. Thus, ROT inhibition of mitochondrial electron transport may be insufficient to induce apoptosis in PW cells. Instead, apoptosis in these cells occurs as a consequence of disruption of the cell cycle and is only indirectly dependent upon mitochondrial electron transport.

Radioimmunotherapy of B-cell NHL

Much progress has been made in the development and implementation of radionuclide-carrying antibody therapy (radioimmunotherapy or RIT) of non-Hodgkin's lymphomas (NHL) in the past decade. Response rates have generally exceeded 60% for nonmyeloablative single dose RIT (85% - 100% for myeloablative) in patients who have relapsed after primary therapy. It is also encouraging that the duration of such responses has often been greater than the response to the last chemotherapeutic regimen administered. These results, as well as a favorable toxicity profile, have resulted in the successful earlier and more widespread use of this new therapeutic modality. Although unlabeled antibody therapy alone has had a positive impact on the treatment of NHL, the response rates for RIT have been higher than (sometimes nearly double) those for unlabeled antibody therapy. This has been demonstrated in trials that have directly compared radiolabeled antibody with unlabeled antibody, as well as in separate trials for similar patient groups. Use of radionuclides in conjunction with antibodies adds transient marrow suppression and a small risk of second malignancy over unlabeled antibody therapy. However, the toxicity from a single course of RIT is very favorable compared to chemotherapy. Despite the enormous progress of RIT, much remains to be learned to fully optimize the role of this exciting modality in the treatment of NHL.

Pivotal study of iodine I 131 tositumomab for chemotherapy-refractory low-grade or transformed low-grade B-cell non-Hodgkin's lymphomas

PURPOSE

To evaluate the efficacy and safety of tositumomab and iodine I 131 tositumomab (Bexxar; Corixa Corp, Seattle, WA, and GlaxoSmithKline, Philadelphia, PA) in patients with chemotherapy-refractory low-grade or transformed low-grade non-Hodgkin's lymphoma (NHL) and to compare its efficacy to the patients' last qualifying chemotherapy (LQC) regimens.

PATIENTS AND METHODS

Sixty patients who had been treated with at least two protocol-specified qualifying chemotherapy regimens and had not responded or progressed within 6 months after their LQC were treated with a single course of iodine I 131 tositumomab.

RESULTS

Patients had received a median of four prior chemotherapy regimens. A partial or complete response (CR) was observed in 39 patients (65%) after iodine I 131 tositumomab, compared with 17 patients (28%) after their LQC (P <.001). The median duration of response (MDR) was 6.5 months after iodine I 131 tositumomab, compared with 3.4 months after the LQC (P <.001). Two patients (3%) had a CR after their LQC, compared with 12 (20%) after iodine I 131 tositumomab (P <.001). The MDR for CR was 6.1 months after the LQC and had not been reached with follow-up of more than 47 months after iodine I 131 tositumomab. An independent review panel verified that 32 (74%) of the 43 patients with nonequivalent durations of response (> 30 days difference) had a longer duration of response after iodine I 131 tositumomab (P <.001). Only one patient was hospitalized for neutropenic fever. Five patients (8%) developed human antimurine antibodies, and one (2%) developed an elevated TSH level after treatment. Myelodysplasia was diagnosed in four patients in follow-up.

CONCLUSION

A single course of iodine I 131 tositumomab was significantly more efficacious than the LQC received by extensively pretreated patients with chemotherapy-refractory, low-grade, or transformed low-grade NHL and had an acceptable safety profile.

Bcl-2 inhibits apoptosis induced by mitochondrial uncoupling but does not prevent mitochondrial transmembrane depolarization

Bcl-2 overexpression protects cells from apoptosis induced by many cytotoxic agents. In this study, we investigated the effects of uncoupling mitochondrial electron transport in both HL60 wild-type and Bcl-2-overexpressing cells using the protonophore carbonyl cyanide m-chlorophenylhydrazone. We found that uncoupling mitochondrial electron transport induced apoptosis in wild-type, but not in Bcl-2-overexpressing cells. To investigate the mechanism of action of Bcl-2-mediated inhibition of cyanide m-chlorophenylhydrazone-induced apoptosis, we measured the mitochondrial transmembrane potential (DeltaPsi(m)) after uncoupling mitochondrial electron transport and found that both HL-60 wild-type and Bcl-2-overexpressing cells similarly depolarize following cyanide m-chlorophenylhydrazone exposure. Western blot analysis demonstrated that Bcl-2 overexpression did not completely block cytochrome c release from mitochondria after uncoupling mitochondrial electron transport. Since Bcl-2 may act as an antioxidant, we studied the effect of altering the cellular redox state prior to uncoupling mitochondrial electron transport in Bcl-2-overexpressing cells. Depletion of mitochondrial (but not cytosolic) glutathione induced apoptosis in Bcl-2-overexpressing cells and negated the protective effect of Bcl-2. Furthermore, following glutathione depletion, Bcl-2-overexpressing cells were sensitized to undergo cyanide m-chlorophenylhydrazone-induced apoptosis. These data suggest that the action of Bcl-2 is dependent, in part, on the cellular and mitochondrial redox state.

Long-term follow-up of patients with Stage III follicular lymphoma treated with primary radiotherapy at Stanford University

PURPOSE

To report the long-term survival and late toxicity data of Stage III follicular lymphoma patients treated with primary radiotherapy.

METHODS AND MATERIALS

Sixty-six patients with Stage III follicular small cleaved (FSC) or follicular mixed (FM) non-Hodgkin's lymphoma were treated with total lymphoid irradiation (61 patients) or whole body irradiation (5 patients) as their primary treatment modality from 1963 to 1982 at Stanford University. Adjuvant chemotherapy was given to 13 patients.

RESULTS

Median follow-up was 9.5 years with a range of 0.5-24.3 years. Median overall survival, cause-specific survival, freedom from relapse, and event-free survival were 9.5, 18.9, 7.1, and 5.1 years, respectively. Few initial relapses or lymphoma-related deaths were seen beyond the first decade of follow-up. Patient age and number of disease sites were the two strongest predictors of overall survival. The cohort of patients with limited Stage III disease demonstrated an 88% freedom from relapse and a 100% cause-specific survival with up to 23.5 years follow-up.

CONCLUSION

The long-term survival data for Stage III FSC or FM non-Hodgkin's lymphoma treated with primary radiotherapy are at least comparable and possibly better than results achieved with other therapeutic approaches. Patients with limited Stage III disease do particularly well. Whether these results are superior to an initial approach of deferred therapy until clinically indicated is currently unknown.

Radiation induces upregulation of cyclooxygenase-2 (COX-2) protein in PC-3 cells

PURPOSE

To investigate the impact of gamma-irradiation on cyclooxygenase-2 (COX-2) expression and its enzymatic activity in PC-3 cells. Cell cycle redistribution, viability, and apoptosis were quantitated in control and irradiated cells with or without the COX-2 inhibitor NS-398.

METHODS AND MATERIALS

Western blot analysis was used to assess COX-2 protein expression. Prostaglandin (PGE(2)) was measured after addition of arachidonic acid (AA) using a Monoclonal Immunoassay Kit. Cell cycle and apoptosis were assessed using flow cytometry.

RESULTS

We observed a dose-dependent increase in COX-2 of 37.0%, 79.7%, and 97.5% following irradiation with 5, 10, and 15 Gy, respectively. The PGE(2) level of irradiated cells was higher than in controls (1512 +/- 157.5 vs. 973.7 +/- 54.2 rhog PGE(2)/mL; p < 0.005, n = 4) while cells irradiated in the presence of NS-398 had reduced PGE(2) levels (218.8 +/- 80.1 rhog PGE(2)/mL; p < 0.005; n = 4). We found no differences in cell cycle distribution or apoptosis between cells irradiated in the presence or absence of NS-398.

CONCLUSIONS

COX-2 protein is upregulated and enzymatically active after irradiation, resulting in elevated levels of PGE(2). This effect can be suppressed by NS-398, which has clinical implications for therapies combining COX-2 inhibitors with radiation therapy.

Bcl-2 overexpression results in enhanced capacitative calcium entry and resistance to SKF-96365-induced apoptosis

Although there is evidence that changes in cellular ionic concentrations are important early events in apoptosis, the regulation of ion fluxes across the plasma membrane during this process is poorly understood. We report here that Bcl-2 overexpression results in up-regulation of capacitative Ca2+ entry (CCE) and that SKF-96365, an inhibitor of CCE, is a potent inducer of apoptosis. Cells that overexpress Bcl-2 are resistant to SKF-96365-mediated apoptosis and to its inhibition of CCE. Enhanced CCE can be reversed with ouabain, suggesting that Bcl-2-associated plasma membrane hyperpolarization plays a role in up-regulating CCE and may partially explain the antiapoptotic effect of Bcl-2.

Clinical radioimmunotherapy

Radioimmunotherapy (RIT) is a promising new therapy for the treatment of a variety of malignancies. General principles of RIT are discussed, including important considerations in the selection of monoclonal antibodies (MAb) and radionuclides for RIT. Results of clinical trials using RIT for the treatment of lymphoma, leukemia, and solid tumors are summarized. The results from many of these trials are promising, especially for the treatment of lymphohematopoietic malignancies, in which a variety of MAb, radionuclides, and study designs have resulted in high response rates with a number of durable responses. Encouraging results have also been obtained using RIT to treat some solid tumors, primarily in patients with relatively low tumor burdens. RIT is generally well tolerated, with the primary toxicity being transient reversible myelosuppression in most nonmyeloablative studies. Nonhematologic toxicity, especially at nonmyeloablative doses, has been minimal in most studies. Approaches for increasing the therapeutic index of RIT are reviewed, which may further potentiate the efficacy and decrease the toxicity of RIT.

Multicenter phase II study of iodine-131 tositumomab for chemotherapy-relapsed/refractory low-grade and transformed low-grade B-cell non-Hodgkin's lymphomas

PURPOSE

This multicenter phase II study evaluated the efficacy, dosimetry methodology, and safety of iodine-131 tositumomab in patients with chemotherapy-relapsed/refractory low-grade or transformed low-grade non-Hodgkin's lymphoma (NHL).

PATIENTS AND METHODS

Patients received a dosimetric dose that consisted of 450 mg of anti-B1 antibody followed by 35 mg (5 mCi) of iodine-131 tositumomab. Serial total-body gamma counts were then obtained to calculate the patient-specific millicurie activity required to deliver the therapeutic dose. A therapeutic dose of 75 cGy total-body dose (attenuated to 65 cGy in patients with platelet counts of 101,000 to 149,000 cells/mm(3)) was given 7 to 14 days after the dosimetric dose.

RESULTS

Forty-five of 47 patients were treated with a single dosimetric and therapeutic dose. Twenty-seven patients (57%) had a response. The response rate was similar in patients with low-grade (57%) or transformed low-grade (60%) NHL. The median duration of response was 9.9 months. Fifteen patients (32%) achieved a complete response (CR; 10 CRs and five clinical CRs), including five patients (50%) with transformed low-grade NHL. The median duration of CR was 19.9 months, and six patients have an ongoing CR. Treatment was well tolerated, with the principal toxicity being hematologic. The most common nonhematologic toxicities that were considered to be possibly related to the treatment included mild to moderate fatigue (32%), nausea (30%), fever (26%), vomiting (15%), infection (13%), pruritus (13%), and rash (13%). Additionally, one patient developed human-antimouse antibodies.

CONCLUSION

Iodine-131 tositumomab produced a high overall response rate, and approximately one third of patients had a CR despite having chemotherapy-relapsed or refractory low-grade or transformed low-grade NHL.

Phase II trial of yttrium-90-DOTA-biotin pretargeted by NR-LU-10 antibody/streptavidin in patients with metastatic colon cancer

A Phase II study of yttrium-90-tetra-azacyclododecanetetra-acetic acid-biotin (90Y-DOTA-biotin) pretargeted by NR-LU-10 antibody/streptavidin (SA) was performed. The primary objectives of the study were to evaluate the efficacy and safety of this therapy in patients with metastatic colon cancer. Twenty-five patients were treated with a single dose of 110 mCi/m2 (mean administered dose, 106.5 +/- 10.3 mCi/m2) of 90Y-DOTA-biotin. There were three components of the therapy. Patients first received NR-LU-10/SA on day 1. A clearing agent (biotin-galactose-human serum albumin) was administered approximately 48 h after the NR-LU-10/SA to remove residual circulating unbound NR-LU-10/SA. Lastly, 24 h after administration of clearing agent, patients received biotin-DOTA-labeled with 110 mCi/m2 90Y. All three components of the therapy were administered i.v. Both hematological and nonhematological toxicities were observed. Diarrhea was the most frequent grade 4 nonhematological toxicity (16%; with 16% grade 3 diarrhea). Hematological toxicity was less severe with 8% grade 3 and 8% grade 4 neutropenia and 8% grade 3 and 16% grade 4 thrombocytopenia. The overall response rate was 8%. Two partial responders had freedom from progression of 16 weeks. Four patients (16%) had stable disease with freedom from progression of 10-20 weeks. Despite the relatively disappointing results of this study in terms of therapeutic efficacy and toxicity, proof of principle was obtained for the pretargeting approach. In addition, valuable new information was obtained about normal tissue tolerance to low-dose-rate irradiation that will help to provide useful guidelines for future study designs.

G2/M-phase arrest and death by apoptosis of HL60 cells irradiated with exponentially decreasing low-dose-rate gamma radiation

Cells of the TP53-deficient human leukemia cell line HL60 continue to progress throughout the cell cycle and arrest in the G2/M phase during protracted exposure to exponentially decreasing low-dose-rate radiation. We have hypothesized that G2/M-phase arrest contributes to the extent of radiation-induced cell death by apoptosis as well as to overall cell killing. To test this hypothesis, we used caffeine and nocodazole to alter the duration of G2/M-phase arrest of HL60 cells exposed to exponentially decreasing low-dose-rate irradiation and measured the activity of G2/M-phase checkpoint proteins, redistribution of cells in the phases of the cell cycle, cell death by apoptosis, and overall survival after irradiation. The results from these experiments demonstrate that concomitant exposure of HL60 cells to caffeine (2 mM) during irradiation inhibited radiation-induced tyrosine 15 phosphorylation of the G2/M-phase transition checkpoint protein CDC2/p34 kinase and reduced G2/M-phase arrest by 40-46% compared to cells irradiated without caffeine. Radiation-induced apoptosis also decreased by 36-50% in cells treated with caffeine and radiation compared to cells treated with radiation alone. Radiation survival was significantly increased by exposure to caffeine. In contrast, prolongation of G2/M-phase arrest by pre-incubation with nocodazole enhanced radiation-induced apoptosis and overall radiation-induced cell killing. To further study the role of cell death by apoptosis in the response to exponentially decreasing low-dose-rate irradiation, HL60 cells were transfected with the BCL2 proto-oncogene. The extent of G2/M-phase arrest was similar for parental, neomycin-transfected control and BCL2-transfected cells during and after exponentially decreasing low-dose-rate irradiation. However, there were significant differences (P < 0.01) in the extent of radiation-induced apoptosis of parental and neomycin- and BCL2-transfected cells after irradiation, with significantly less radiation-induced apoptosis and higher overall survival in BCL2-transfected cells than similarly irradiated control cells. These data demonstrate that radiation-induced G2/M-phase arrest and subsequent induction of apoptosis play an important role in the response of HL60 cells to low-dose-rate irradiation and suggest that it may be possible to increase radiation-induced apoptosis by altering the extent of G2/M-phase arrest. These findings are clinically relevant and suggest a novel therapeutic strategy for increasing the efficacy of brachytherapy and radioimmunotherapy.

Radiosensitization by intratumoral administration of cisplatin in a sustained-release drug delivery system

PURPOSE

Effects of combining local irradiation and intratumoral (i.t.) administration of cisplatin (CDDP) in a sustained-release drug delivery system (epi gel) were studied in a murine SCCVII squamous cell carcinoma model in mice.

MATERIALS AND METHODS

The epinephrine injectable gel was used as a drug delivery system. Intratumoral pharmacokinetics of CDDP was studied by using 195mPt-CDDP. The tumor volume quadrupling time (TVQT) and tumor growth delay (TGD) time were used to evaluate the antitumor efficacy of treatment regimens.

RESULTS

The concentration and residence of 195mPt-CDDP was significantly higher in tumors treated with 195mpt-CDDP/epi gel than in tumors treated with 195mPt CDDP gel or 195mPt-CDDP suspension. Intratumoral administration of CDDP/epi gel (4 mg/kg) produced an average TGD time of 15.5 +/- 2.8 days, which was 5.2 - 7.4 times longer than CDDP suspension i.t. or i.p. When combined with a single dose of radiation (10 Gy), i.t. administration of CDDP/epi gel was 2.0 - 3.6-fold as effective as administered i.t. in suspension (39.2 +/- 4.1 vs. 19.8 +/- 3.9 days of TGD, P < 0.05) or i.p. in solution (39.2 +/- 4.1 vs. 11.0 +/- 1.6 days, P < 0.001) in inhibiting tumor growth and produced 20-60% complete remission of tumors. When combined with fractionated irradiation, pre-irradiation CDDP administration was more effective than post-radiation administration (26.7 vs. 12.1 days of TGD, P < 0.05). Mice treated with CDDP/epi gel i.t. alone or in combination with irradiation, had little systemic toxicity.

CONCLUSIONS

Intratumoral administration of CDDP using the sustained-release drug delivery system is an efficient and safe method to maximize the drug concentration in tumor, minimize the systemic toxicity and enhance antitumor efficacy of irradiation.

Myc activation reduces fibroblast clonogenicity via an apoptotic mechanism that can be suppressed by a soluble paracrine factor

The c-Myc transcription factor is involved in the regulation of cellular proliferation and differentiation and is one of the most frequently deregulated genes in human cancers. While c-Myc is known to enhance the proliferative potential of cells, its activation in immortalized fibroblasts has been found to result in apoptosis following gamma-irradiation or under adverse growth conditions, including serum deprivation and hypoxia. When plating Rat-1 fibroblasts at low cell densities (100 cells/100 mm plate), we observed a substantial reduction in the clonogenicity of cells with deregulated c-Myc activity compared to cells with normal c-Myc activity. This difference in clonogenicity was apparent despite the fact that cells were plated in media containing sufficient serum and oxygen concentrations known to suppress apoptosis of exponentially growing Rat-1 fibroblasts with activated c-Myc. Therefore, we hypothesized that the observed reduction in plating efficiency in cells with activated c-Myc occurred via an apoptotic mechanism and that a fibroblast-derived factor was required for suppression of apoptosis. Overexpression of the anti-apoptotic oncogene, Bcl-2, in cells with activated c-Myc restored the plating efficiency to normal levels in cells plated at low cell densities. This strongly suggested that the decreased clonogenicity of fibroblasts with altered c-Myc activity resulted from enhanced apoptosis of the cells under these conditions. Furthermore, plating cells on a feeder layer of lethally-irradiated fibroblasts or in Rat-1 conditioned media increased the plating efficiencies of sparsely plated cells in a dose-dependent fashion. These results suggest that in addition to previously reported requirements for serum-derived growth factors and normal oxygen conditions, a paracrine factor liberated by Rat-1 fibroblasts is required to suppress c-Myc-induced apoptosis in these cells.

Direct evidence that apoptosis enhances tumor responses to fractionated radiotherapy

Currently, the contribution of cellular apoptotic sensitivity to tumor response after radiation therapy remains controversial. To address this issue, the survival of Rat-1 fibroblasts containing a 4-hydroxytamoxifen-regulated c-Myc allele, c-MycER (T. D. Littlewood et al., Nucleic Acids Res., 23: 1686-1690, 1995), after single and fractionated doses of radiation was investigated. This model system allows pharmacological regulation of apoptosis sensitivity in the same cells in vitro and as xenograft tumors derived from these cells in vivo (G. I. Evan et al., Cell, 69: 119-128, 1992; R. M. Alarcon et al., Cancer Res., 56: 4315-4319, 1996). Activating c-MycER in vitro resulted in marked sensitization of Rat-1 fibroblasts to the effects of both single-dose and fractionated irradiation as measured by the induction of apoptosis and clonogenic survival. Overexpression of the antiapoptosis protein Bcl-2 suppressed the induction of apoptosis and increased clonogenic survival in cells with activated c-Myc after single-dose and fractionated radiation. Systemic time-release implant delivery of 4-hydroxytamoxifen to severe combined immunodeficient mice bearing Rat-1-MycER tumors over the course of either single-dose (10 Gy) or fractionated (five fractions of 2 Gy) radiotherapy resulted in prolonged tumor growth delay relative to identical tumors from mice that received placebo implants. Furthermore, tumors derived from Rat-1-MycER cells that overexpressed Bcl-2 exhibited shorter tumor growth delays relative to similarly treated Rat-1-MycER tumors. The length of tumor growth delay after single-dose or fractionated radiotherapy strongly correlated with the extent of radiation-induced apoptosis in the xenograft tumors as measured by terminal deoxynucleotidyl transferase-mediated nick end labeling. These in vivo results provide direct evidence that increasing the sensitivity of tumor cells to die by apoptosis increases the efficacy of fractionated radiotherapy by reducing tumor cell clonogenic survival.

p53 mediates apoptosis induced by c-Myc activation in hypoxic or gamma irradiated fibroblasts

Deregulated c-Myc expression leads to a cellular state where proliferation and apoptosis are equally favored depending on the cellular microenvironment. Since the apoptotic sensitivity of many cells is influenced by the status of the p53 tumor suppressor gene, we investigated whether the induction of apoptosis by DNA damage or non-genotoxic stress are also influenced by the p53 status of cells with altered c-Myc activity. Rat-1 fibroblasts expressing a conditional c-Myc allele (c-MycER), were transfected to express an antisense RNA complimentary to p53 mRNA. Expression of antisense p53 RNA decreased p53 protein levels and delayed p53 accumulation following c-Myc activation. Under hypoxic or low serum conditions, cells expressing antisense p53 were substantially more resistant to c-Myc-induced apoptosis than were control cells. c-Myc activation also sensitized Rat-1 cells to radiation-induced apoptosis. Rat-1 cells expressing antisense p53 RNA were more resistant to apoptosis induced by the combined effects of c-Myc activation and gamma irradiation. In a similar manner, apoptosis induced by c-Myc in serum starved, hypoxic or gamma irradiated fibroblasts was also inhibited by Bcl-2. These data indicate that p53 is involved in c-Myc-mediated apoptosis under a variety of stresses which may influence tumor growth, evolution and response to therapy.

Impaired bioavailability of interferon beta-1a when administered intramuscularly by needle-free injection

Intramuscular (IM) or subcutaneous (SC) drug administration of small molecules and protein has been demonstrated by use of needle-free jet injection methods. One device that achieves needle-free parenteral administration, BIOJECTOR, is commercially available and was evaluated for IM delivery of interferon beta-1a. Recombinant human interferon beta-1a (IFN beta-1a) is a glycosylated protein containing 166 amino acids and has a molecular weight of 22.5 kDa. Needle-free jet injection of IFN beta-1a with the BIOJECTOR was assessed in a human Phase I trial. The study was a randomized, open-label crossover in which 12 healthy subjects each received 60 microg of IFN beta-1a as an IM injection by standard needle administration and by needle-free jet injection. Blood samples for pharmacokinetic (serum activity, PK) and pharmacodynamic (serum neopterin, PD) determinations were collected through 144 hours post-dose. Mean serum antiviral activity AUC values for needle-free and standard needle injection were 218 and 531 U x h/ml, respectively; corresponding C(max) values were 19.7 and 29.0 U/ml. Median T(max) following both treatments was 12 hours. The relative bioavailability of IFN beta-1a, needle-free to standard needle injection, was 41.1% with 90% confidence limits of 24.4% to 69.3%. Mean serum neopterin E(AUC) values for needle-free and standard needle injection were 114 and 325 ng x h/mL, respectively; corresponding E(max) values were 2.3 and 5.6 ng/mL. The ratio of serum neopterin E(AUC), needle-free to standard needle, was 34.9% with 90% confidence limits of 23.4% to 52.1%. Injection site reactions were substantially more frequent following needle-free injection; however, systemic side effects were less frequent. Intramuscular needle-free jet injection and needle-based injection of a 22.5-kDa glycoprotein do not produce equivalent systemic PK or PD responses.

Effects of keratinocyte growth factor on the proliferation and radiation survival of human squamous cell carcinoma cell lines in vitro and in vivo

PURPOSE

Keratinocyte growth factor (KGF) has potent mitogenic activity on normal epithelial cells and has been found to enhance intestinal crypt cell survival in irradiated mice and to prevent radiation and chemotherapy-induced mucositis in animal models. The purpose of the study reported here is to investigate the effect of recombinant human KGF on the proliferation and survival of human squamous carcinoma cell lines following irradiation.

METHODS AND MATERIALS

The level of KGF receptor (KGFR) mRNA in normal Balb/Mk cell line and human head and neck squamous carcinoma cell lines was assessed using a RNase protection assay. The clonogenic assay and MTT assay were used to study the proliferative effects of KGF on human tumor cell lines and Balb/MK cell line in vitro. Effects of KGF on in vivo tumor growth and radiosensitivity were studied in three KGFR-positive human squamous cell carcinoma xenografts (FaDu, Detroit 562 and A431) in nude mice, and a murine KGFR-negative melanoma tumor (B16) in Balb/c mice.

RESULTS

Seven of 10 tumor cell lines studied expressed KGFR mRNA. None of these tumor cell lines showed enhanced proliferation when exposed to KGF for 2 days or less. Prolonged exposure to KGF for 7 days or longer resulted in low level stimulation of proliferation in both clonogenic and MTT assays in four of seven KGFR-positive cell lines. Two KGFR-negative cell lines also had a low proliferative response to KGF in a clonogenic assay, but not in the MTT assay. Normal keratinocyte Balb/MK cells, which expressed a moderate level of KGFR mRNA, had a strongly proliferative response to KGF. Its KGF enhancement ratio (KER) of plating efficiency was 24-70 times higher than that of the tumor cells studied (p < 0.001). The KGF-stimulated tumor cell growth was almost completely inhibited by heparin or epidermal growth factor (EGF). There were no significant differences (p > 0.05) in the survival of any of tumor cell lines in the presence or absence of KGF (100 ng/ml) irradiated with doses of 0-15 Gy, and no significant differences (p > 0.05) between the radiobiological parameters D0, Dq, and n number from the SHMT model, alpha, beta, and alpha/beta ratio from the LQ model and SF2 for radiation survival curves for cell lines irradiated in the presence or absence of KGF. Three KGFR-positive human squamous cell carcinoma xenografts in nude mice, and a murine KGFR-negative melanoma tumor in Balb/c mice treated with 1.0 mg/kg of KGF for 3 days grew at the same rate as in untreated mice.

CONCLUSION

The recombinant human KGF resulted in little or no stimulation of the proliferation of human head and neck squamous tumor cell lines and did not affect the radiosensitivity of these cell lines in vitro and in vivo. Therefore, KGF may be of clinical value in preventing radiation-induced mucositis and may have the potential to increase the therapeutic index of radiotherapy for treatment of cancers.

Radiobiologic studies of radioimmunotherapy and external beam radiotherapy in vitro and in vivo in human renal cell carcinoma xenografts

BACKGROUND

Previous studies suggest that the radiobiologic characteristics of in vitro survival curves are important determinants of the response of tumors to both conventional radiotherapy and radioimmunotherapy (RIT). The purpose of this study was to elucidate the relationship between in vitro radiation survival curve parameters and the relative sensitivity of tumor to RIT, exponentially decreasing low dose rate (ED LDR) irradiation and conventional high dose rate (HDR) fractionated external beam radiotherapy.

METHODS

Two human renal cell carcinoma cell lines, Caki-1 and A498, were used in vitro and nude mouse xenograft studies. HDR external beam gamma irradiation (dose rate, 430 centigray [cGy]/minute) and ED LDR irradiation (initial dose rate, 22-25 cGy/hour) were performed with a cesium-137 (137Cs) gamma irradiator. RIT was carried out with yttrium-90 (90Y-labeled monoclonal antibody NR-LU-10, and the absorbed radiation doses were calculated by medical internal radiation dose methodology. A clonogenic assay was used to generate radiation survival curves, and a computer FIT program was used to calculate the radiobiologic parameters. The antitumor efficacy of the different treatments was compared in vivo using a tumor regrowth delay assay in these two tumor xenograft models.

RESULTS

The radiation survival curves showed that the Caki-1 cell line was more sensitive to both HDR and ED LDR irradiation than A498 in vitro. The Caki-1 cell line, compared with A498, had a larger alpha (0.39 vs. 0.15 Gy following HDR and 0.32 vs. 0.21 Gy following ED LDR) and alpha-to-beta ratio (6.92 vs. 2.60 Gy for HDR and 40.0 vs. 19.2 Gy for ED LDR), a smaller n number (5.13 vs. 23 for HDR and 1.16 vs. 3.53 for ED LDR), a lower quasi-threshold dose (Dq) (1.60 vs. 3.15 Gy for HDR and 0.35 vs. 1.76 Gy for ED LDR), and a lower surviving fraction at 2 Gy (SF2) (0.37 vs. 0.60 for HDR and 0.51 vs. 0.61 for ED LDR), suggesting that Caki-1, compared with A498, had a steep initial slope and a small shoulder. The final slope represented by the beta value and D0 dose (the dose (Gy) required to reduce the fraction of surviving cells of 37% of its previous value in the exponential region of the survival curves) did not vary significantly between these two cell lines at either HDR or ED LDR irradiation. Tumor volume doubling times were 4.0 +/- 1.5 days for Caki-1 and 4.2 +/- 1.8 days for A498 tumor xenografts. One hundred microCi/50 microg of 90Y-labeled, isotype-matched irrelevant monoclonal antibody CCOO16-3 produced a tumor growth delay time (TGD) of 2.1 days in Caki-1 tumors but had no effect on A498 tumors (P < 0.05). RIT with 100 microCi of 90Y-NR-LU-10 resulted in a TGD of 4.8 days for Caki-1 tumors, whereas 100 microCi and 150 microCi of 90Y-NR-LU-10 produced a TGD of 1.9 and 2.7 days for A498 tumors, respectively. Estimated absorbed doses were 21.9 Gy in Caki-1 tumors treated with 100 microCi of 90Y-NR-LU-10 and 14.5 Gy and 21.8 Gy in A498 tumors treated with 100 microCi and 150 microCi of 90Y-NR-LU-10, respectively. The weighted normal tissue absorbed doses were 7.4 Gy for Caki-1 tumor-bearing mice and 9.0 Gy for A498 tumor-bearing mice (P > 0.05). To compare the responses of Caki-1 and A498 xenografts to RIT with external beam ED LDR and HDR irradiation, tumor-bearing mice were treated with equivalent doses (20-22 Gy) of 1) RIT with 90Y-NR-LU-10 (100 microCi for Caki-1 and 150 microCi for A498), 2) continuous ED LDR 137Cs irradiation with a initial dose rate of 22 cGy/hour, or 3) HDR X-irradiation (2 Gy x 10 fractions in 2 weeks). The TGDs produced by RIT, ED LDR, and HDR were 5.3, 9.7, and 8.3 days for Caki-1 and 2.7, 5.1, and 5.8 days for A498. The relative efficacy of RIT in these xenograft models correlated well with the radiobiologic parameters (i.e., the size of the initial slope and shoulder) of in vitro survival curves following HDR and ED LDR irradiation in these cell lines. (ABSTRACT TRUNCATED)

Enhancement of murine intestinal stem cell survival after irradiation by keratinocyte growth factor

Radiation-induced gastrointestinal toxicity is due in part to the killing of the clonogenic crypt cells and eventual depopulation of the villi. Keratinocyte growth factor (KGF), a member of the fibroblast growth factor family (FGF-7), has been shown to stimulate proliferation of cells along the murine digestive tract from the foregut to the colon. Using an in vivo microcolony assay, we found that 1.0 mg/kg KGF administered intravenously (i.v.) for 3 consecutive days (2 days before, 1 day before and 2 h after irradiation) increased the number of surviving crypts by a factor of 2.6, 2.7 and 2.4 in the duodenum, jejunum and ileum, respectively, after a single-dose whole-body irradiation (10-16 Gy) (P < 0.001). Treatment of mice with KGF i.v. significantly increased the D0 of the radiation survival curves by 0.37, 0.22 and 0.36 Gy, leading to dose modification factors of 1.28, 1.16 and 1.24 for duodenal, jejunal and ileal crypt cells, respectively. Similar results were obtained with KGF administered subcutaneously. Treatment with both KGF and stem cell factor (previously shown to enhance intestinal crypt survival after total-body irradiation) increased the number of surviving crypt cells after irradiation to levels similar to that in animals treated with KGF alone. Administration of KGF for 7 consecutive days (beginning 2 days prior to irradiation) increased the LD(50/10) from 5.50 Gy/day to 5.90 Gy/day (P = 0.05) for animals irradiated with five daily fractions to a local abdominal field. These results suggest that KGF may be of clinical value in reducing radiation toxicity to the intestine.