Incident HIV-Associated Wasting/Low Weight Is Associated with Nearly Doubled Mortality Risk in the Modern ART Era

HIV-associated wasting (HIVAW) is an underappreciated AIDS-defining illness, despite highly effective antiretroviral therapy (ART). We (a) assessed the association between incident HIVAW/low weight and all-cause mortality and (b) described virologic outcomes after people with HIV (PWH) experienced HIVAW/low weight while on ART. In the Observational Pharmaco-Epidemiology Research & Analysis (OPERA®) cohort, PWH without prior HIVAW/low weight who were active in care in 2016-2020 were followed through the first of the following censoring events: death, loss to follow-up, or study end (October 31, 2021). HIVAW/low weight was a diagnosis of wasting or low body mass index (BMI)/underweight or a BMI measurement <20 kg/m2. Hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between time-dependent HIVAW/low weight and mortality were estimated with extended Cox regression models. Over a median follow-up of 45 months (interquartile range: 27, 65), there were 4,755 (8%) cases of HIVAW/low weight and 1,354 (2%) deaths among 62,314 PWH. PWH who experienced HIVAW/low weight had a significantly higher risk of death than those who did not (HR: 1.96; 95% CI: 1.68, 2.27) after adjusting for age, race, ethnicity, and changes in viral load (VL) and Veterans Aging Cohort Study Mortality Index scores over follow-up. Among 4,572 PWH on ART at HIVAW/low weight, 68% were suppressed (VL of <200 copies/mL); subsequent virologic failure was uncommon (7%). Among viremic PWH, 70% and 60% achieved suppression and undetectability (VL of <50 copies/mL), respectively, over follow-up. HIVAW remains a challenge for some PWH. Particular attention needs to be paid to HIVAW/low weight and virologic control to restore health and potentially reduce the risk of death.

Improving Adherence to the Target Window for Cabotegravir + Rilpivirine Long-Acting Injections Through the CHORUS™ App and Web Portal: A Cluster Randomized Trial

BACKGROUND

We evaluated the impact of the CHORUS™ app on adherence to the cabotegravir and rilpivirine long-acting injectable (CAB + RPV LAI) monthly injections schedule.

METHODS

Healthcare centers (HCCs) were randomized to access CHORUS™ CAB + RPV LAI features (intervention) or not (control) from 01OCT2021-31JAN2022. Target window adherence (maintenance injections ≤7 days before/after target day) was assessed with multivariate logistic regression (generalized estimating equations).

RESULTS

CAB + RPV LAI was administered to 188 and 79 individuals at intervention and control HCCs, respectively. Intervention was not associated with improved target window adherence (adjusted odds ratio: 0.61 [95% CI: 0.30-1.25]). However, app use was associated with increased odds of adherence compared to no app use among all intervention HCCs (2.98 [1.26-7.06]) and at smaller HCCs (3.58 [1.31-9.80]).

CONCLUSIONS

While access to CHORUS™ CAB + RPV LAI features did not improve target window adherence, app use did, especially at smaller HCCs which may not have established LAI management procedures.

TRIAL REGISTRATION

https://clinicaltrials.gov/show/NCT04863261.

Cabotegravir + Rilpivirine Long-Acting Injections for HIV Treatment in the US: Real World Data from the OPERA Cohort

INTRODUCTION

The first complete long-acting antiretroviral therapy (ART) regimen, cabotegravir + rilpivirine long-acting (CAB + RPV LA) injectable, was approved in the US for HIV-1 treatment in individuals on a stable antiretroviral regimen with a viral load < 50 copies/mL, no treatment failure history, and no resistance to either cabotegravir or rilpivirine. We describe injection schedule adherence and virologic effectiveness of CAB + RPV LA in routine clinical care in the US.

METHODS

From the OPERA® cohort, all adults with HIV who received their first CAB + RPV LA injection and ≥ 1 continuation injections between 21 January 2021 and 15 March 2022 were included. The injection target date was updated monthly and set to the same date of the month as the previous injection. Continuation injections administered within 7 days before or after the target date were considered on time, as per the label. Virologic undetectability (viral load < 50 copies/mL), suppression (viral load < 200 copies/mL), and confirmed virologic failure (2 consecutive viral loads ≥ 200 copies/mL or 1 viral load ≥ 200 copies/mL followed by discontinuation) were described among individuals with a viral load < 50 copies/mL at initiation and ≥ 1 follow-up viral load.

RESULTS

Among 321 individuals on CAB + RPV LA, 90% of the continuation injections were administered on time (within ± 7 days of the target date). Of the 237 individuals with a viral load < 50 copies/mL at initiation and ≥ 1 follow-up viral load, nearly all were undetectable (95%) or suppressed (99%) at their last viral load measurement, 96% maintained virologic suppression with all measured viral loads < 200 copies/mL, and four confirmed virologic failures were observed. Injection delays were infrequent, and did not affect virologic outcomes over the short term.

CONCLUSION

In this large US cohort, most monthly CAB + RPV LA injections were administered on time and high levels of virologic control were achieved. These results suggest that CAB + RPB LA injectable can be administered effectively during routine clinical care.

Definition, Burden, and Predictors of HIV-Associated Wasting and Low Weight in the OPERA Cohort

We aimed to describe the prevalence, incidence, and predictors of HIV-associated wasting (HIVAW)/low weight among people with HIV (PWH) in the United States. We conducted an observational, clinical cohort analysis, utilizing prospectively collected electronic health record data obtained from the Observational Pharmaco-Epidemiology Research & Analysis (OPERA®) cohort. HIVAW/low weight included a wasting or low body-mass index (BMI)/underweight diagnosis (ICD codes and title search) or BMI <20 kg/m2. Prevalence was estimated among adult PWH in care from 2012 to 2015 and 2016 to 2020. Incidence from January 1, 2016, to October 31, 2021, was estimated using univariate Poisson regression among eligible PWH without prior HIVAW/low weight. Demographic and clinical predictors of incident HIVAW/low weight were included in multivariable logistic regression models, stratified by antiretroviral therapy (ART) experience. The period prevalence of HIVAW/low weight was 12% in both 2012-2015 and 2016-2020. Among 67,119 PWH without any prior HIVAW/low weight, 7% experienced incident HIVAW/low weight a median 64 months from HIV diagnosis. In multivariable regression models, similar predictor patterns were observed among ART-naïve and ART-experienced PWH without any prior HIVAW/low weight: lower odds of HIVAW/low weight with older age, female sex, Black race, and Hispanic ethnicity and higher odds with Medicaid. Notably, there was a dose-response relationship between increasing Veterans Aging Cohort Study Mortality Index scores and incident HIVAW/low weight in both groups. Wasting/low weight remains a challenge for PWH and may be underappreciated by providers. Advanced HIV and comorbidities significantly predict incident HIVAW/low weight. Increasing awareness of HIVAW, especially among frailer PWH, could improve the care of affected PWH.

Heavily treatment-experienced people living with HIV in the OPERA® cohort: population characteristics and clinical outcomes

BACKGROUND

Multi-class resistance, intolerance, and drug-drug interactions can result in unique antiretroviral (ART) combinations for heavily treatment-experienced (HTE) people living with HIV (PLWH). We aimed to compare clinical outcomes between HTE and non-HTE PLWH.

METHODS

Eligible ART-experienced PLWH in care in the OPERA® Cohort were identified in a cross-sectional manner on December 31, 2016 and observed from the date of initiation of the ART regimen taken on December 31, 2016 until loss to follow up, death, study end (December 31, 2018), or becoming HTE (non-HTE group only). In the absence of resistance data, HTE was defined based on the ART regimens used (i.e., exposed to ≥ 3 core agent classes or regimen suggestive of HTE). Time to virologic undetectability, failure, and immunologic preservation were assessed using Kaplan-Meier methods; cumulative probabilities were compared between the two groups. Regimen changes, incident morbidities, and death were described.

RESULTS

A total of 24,183 PLWH (2277 HTE PLWH, 21,906 non-HTE) were followed for a median of 28 months (IQR 21, 38). Viremic HTE PLWH (viral load [VL] ≥ 50 copies/mL) were less likely to achieve undetectability (VL < 50 copies/mL; 24-month cumulative probability: 80% [95% Confidence Interval 77-82]) than their non-HTE counterparts (85% [84-86]). No difference was observed in the probability of maintaining VLs < 200 copies/mL over the first 48 months after achieving suppression (< 50 copies/mL). HTE PLWH were less likely than non-HTE PLWH to maintain CD4 cell counts ≥ 200 cells/µL (24-month cumulative probability: 95% HTE [91-93]; 97% non-HTE [97-97]), and more likely to change regimens (45% HTE; 41% non-HTE). Incident non-AIDS defining event (ADE) morbidities were common in both populations, though more likely among HTE PLWH (45%) than non-HTE PLWH (35%). Incident ADE morbidities and deaths were uncommon among HTE (ADEs 5%; deaths 2%) and non-HTE (ADEs 2%; deaths 1%) PLWH.

CONCLUSIONS

HTE PLWH were at greater risk of unfavorable treatment outcomes than non-HTE PLWH, suggesting additional therapeutic options are needed for this vulnerable population.

1288. US Healthcare Provider Perspectives on the initiation of cabotegravir and rilpivirine long-acting (CAB+RPV LA) in an observational real-world study (BEYOND)

Background

CAB+RPV LA is a complete regimen for treatment of virologically suppressed people with HIV (PWH). As an injectable therapeutic administered by a healthcare provider (HCP), CAB+RPV LA may alleviate challenges with adherence to daily oral therapy and reduce fear of HIV status disclosure with oral treatment. Real world perspectives from HCPs and PWH are needed to enable successful delivery of this treatment in US healthcare settings.

Methods

BEYOND is a 2 year prospective, observational, real-world study of utilization, outcomes, and experience of PWH initiating CAB+RPV LA across 30 US sites. HCPs at participating sites (treaters, injectors, drug acquisition/reimbursement staff) completed surveys at site activation (Sep 2021-Feb 2022; with follow-up surveys planned at 6, 12, 24 months) evaluating experiences to date with implementation of CAB+RPV LA at their sites.

Results

HCPs from 24 sites responded to the initial survey (Table 1). 75% of HCPs estimated that ≥25% of their PWH are eligible for CAB+RPV LA, and 71% of sites are proactively discussing the regimen with ≥25% of PWH. The majority (79%) of treaters reported they were extremely/very positive about administering CAB+RPV LA. Over 90% of injectors reported a positive overall opinion about administering CAB+RPV LA, and 86% reported the injections were easy to administer. Most (87%) HCPs reported injection visits taking ≤45 minutes, including waiting time. Over 95% of sites have patient reminder systems; 86% will manually identify missed injections and all reported manual follow up by site staff. All sites utilizing the injection education video on the external HCP website (n=15/15) found it helpful and 94% (n=16/17) utilizing reimbursement specialists found them to be helpful. In their experience to date, most clinics reported only needing to increase coordination with the pharmacy team and add injection training to implement CAB+RPV LA. The most frequently reported benefits of implementing CAB+RPV LA by HCPs included assurance of patient adherence and patient engagement in their HIV treatment (Table 2).

Conclusion

Early real-world data from US HCPs in this study indicates interest in and anticipated uptake of CAB+RPV LA at their sites, positive overall opinion, and multiple benefits of administering the CAB+RPV LA regimen to PWH.

Disclosures

Ricky K. Hsu, MD, Gilead: Honoraria|Merck: Honoraria|ViiV: Advisor/Consultant|ViiV: Grant/Research Support|ViiV: Honoraria John Phoenix, MSN, APRN, FNP-C, Gilead Sciences: Advisor/Consultant|Gilead Sciences: Honoraria|Gilead Sciences: speaker bureau, research funding|Janssen Pharmaceutical: Advisor/Consultant|Janssen Pharmaceutical: Honoraria|Lupin Pharmaceuticals: Advisor/Consultant|Lupin Pharmaceuticals: Honoraria|Napo pharmaceutical: Honoraria|Napo pharmaceutical: speaker bureau|Scinexis: Advisor/Consultant|Scinexis: Honoraria|ViiV Healthcare: Advisor/Consultant|ViiV Healthcare: Honoraria|ViiV Healthcare: speaker bureau, clinical research funding Gary I. Sinclair, MD, ABBVIE: Grant/Research Support|Gilead: Grant/Research Support|Janssen: Advisor/Consultant|Janssen: Grant/Research Support|Janssen: Honoraria|Merck: Grant/Research Support|Thera: Grant/Research Support|Thera: Honoraria|ViiV/GSK: Advisor/Consultant|ViiV/GSK: Grant/Research Support|ViiV/GSK: Honoraria Samir K. Gupta, MD, Gilead Sciences: Advisor/Consultant|GSK/ViiV: Advisor/Consultant|GSK/ViiV: Grant/Research Support Ana Puga, MD, FAAP, AAHIVS, Care Resource: Healthcare provider (HCP)|ViiV Healthcare: Stocks/Bonds Kaitlin Nguyen, PharmD, AAHIVE, ViiV Healthcare: Stocks/Bonds Catherine K. Schubert, PharmD, ViiV Healthcare: Stocks/Bonds Deanna Merrill, PharmD, MBA, AAHIVP, ViiV Healthcare: Salaried employee|ViiV Healthcare: Stocks/Bonds David Richardson, BA, ViiV Healthcare: ViiV provided funding to RTI for the development of the study materials, the conduct of the study, and analysis & interpretation of study results. Kate Nelson, M.Ed, ViIV: ViiV provided funding to RTI for the development of the study materials, the conduct of the study, and analysis & interpretation of study results. Maria Reynolds, MStat, ViiV Healthcare: Viiv provided funding to RTI for the development of the study materials, the conduct of the study, and analysis & interpretation of study results. Laurie Zografos, BS, Viiv: ViiV provided funding to RTI for the development of the study materials, the conduct of the study, and analysis & interpretation of study results. Ashley Jean-Louis, MPH, ViiV Healthcare: (ViiV provided funding to RTI for the development of the study materials, the conduct of the study, and analysis & interpretation of study results.) Cindy Garris, MS, ViiV Healthcare: Employee|ViiV Healthcare: Stocks/Bonds.

1951. Guiding COVID-19 Booster Vaccinations by COVID-19 Quantitative Spike Ig Antibody Titers Regardless of HIV Status, Immunosuppression, and Age

Background

In-vitro neutralizing antibody (Ab) titers correlated with ∼250 IU/mL Spike Ig Ab level for the Delta COVID-19 variant, establishing the 2021 French and Swiss cutoff for booster guidance. In a New York City healthcare clinic where those guidelines were adopted, we aimed to quantify vaccination responses in HIV+ and HIV- individuals to assess the utility of quantifying antibodies to guide booster timing.

Methods

Adults who were fully vaccinated against SARS-CoV-2 virus (i.e., 2 Pfizer, 2 Moderna or 1 J&J vaccine) were included if >1 Roche SARS-CoV-2 Semi-Quant Spike Ig Ab test was performed >21 days after vaccination and before any booster (through 03DEC2021). Vaccine response was assessed at the first Ab test and considered adequate (>250 IU/mL) or inadequate (low: ≥51 to ≤250 IU/mL; no response: < 51 IU/mL). The rate of Ab decline was estimated with linear regression, using all sequential Ab tests over the first 6 months between vaccination and boosting. Analyses were stratified by vaccine type, HIV status and CD4 count in HIV+ ( >200 cells/µL cutoff).

Results

Out of 1979 patients, 869 completed their primary vaccinations, of whom 825 (95%) had ≥1 eligible Ab test (HIV+: 512; HIV-: 313; Table). Overall, 83% had an adequate immune response to vaccination (Pfizer: 82%, Moderna: 94%, J&J: 51%), with similar findings regardless of HIV status and CD4 count (Figure 1). In those with ≥2 Ab tests within six months between vaccination and boosting, Ab levels declined at a rate of 91 IU/mL per month (95% CI: -138, -44). While some variation was observed, rates of Ab decay were generally consistent across vaccine, HIV status and CD4 count strata (Figure 2). Only 1/7 breakthrough COVID-19 infections occurred post booster (6 days later).

Conclusion

In the pre-omicron era, primary COVID immunization with a mRNA vaccine generally yielded adequate Ab responses, although inadequate responses were observed in 19% of Pfizer, 6% of Moderna, and 49% of J&J vaccine recipients. Ab levels decreased at an average rate of 91 IU/mL per month after primary immunization. Variability in vaccine responses and Ab declines show the utility of measuring spike Ig Ab levels rather than using empiric time frames for booster guidance. Omicron-specific quantitative IgG neutralization levels must be established to inform preventative care.

Disclosures

Ricky K. Hsu, MD, Gilead: Honoraria|Merck: Honoraria|ViiV: Advisor/Consultant|ViiV: Grant/Research Support|ViiV: Honoraria Laurence Brunet, PhD, AIDS Healthcare Foundation: Client of my employer|EMD Serono: Client of my employer|Gilead Sciences: Client of my employer|Janssen: Client of my employer|Merck & Co: Client of my employer|TheraTechnologies: Client of my employer|ViiV Healthcare: Client of my employer Jennifer S. Fusco, BS, AIDS Healthcare Foundation: Client of my employer|EMD Serono: Client of my employer|Gilead Sciences: Client of my employer|Janssen: Client of my employer|Merck & Co.: Client of my employer|TheraTechnologies: Client of my employer|ViiV Healthcare: Client of my employer.

1264. Durability and effectiveness of fostemsavir in heavily treatment-experienced people with HIV

Background

Paired with other active antiretrovirals (ARVs), fostemsavir (FTR) may offer heavily treatment-experienced (HTE) people with HIV (PWH) options for continuing effective treatment. Durability and effectiveness of FTR-containing regimens in routine clinical care in the United States were assessed.

Methods

Electronic health record data from the OPERA® cohort were used to identify adults initiating FTR-containing regimens between 2JUL2020 (FDA approval) and 1SEP2021. Eligible PWH were followed from first FTR prescription (baseline) until FTR discontinuation, death, loss to follow up, or study end (28FEB2022). Durability was assessed as frequency of FTR discontinuation. Virologic outcomes assessed at 6 and 12 months (±3 months) included suppression (viral load [VL] &lt; 50 copies/mL), virologic failure (2 consecutive VL ≥200 copies/mL or 1 VL ≥200 copies/mL + FTR discontinuation within 120 days after suppression), and viral blips (1 VL ≥50 copies/mL preceded and followed by VLs &lt; 50 copies/mL). Analyses were stratified by baseline viral load (bVL &lt; 50 copies/mL; bVL ≥50 copies/mL).

Results

Overall, 86 PWH initiated FTR (bVL &lt; 50: 30; bVL ≥50: 55), with median follow up of 10.8 months (IQR: 6.8, 15.3). Compared to PWH with bVL ≥50, those with bVL &lt; 50 were older and more likely to be white and have lived longer with HIV (Table 1). Over follow up, 20% discontinued FTR (Table 2). Most (82%) FTR discontinuations were switches to alternative regimens; the remaining were ARV interruptions (no ARVs for &gt; 45 days). Among PWH with bVL &lt; 50, most maintained suppression (6 months: 74%; 12 months: 82%; Figure). Among PWH with bVL ≥50 and with follow up VL during the period assessed, 33% were suppressed at 6 months, 36% were suppressed at 12 months, and 48% achieved suppression at any time over the entire follow up (Figure). In either group, ≤5 PWH experienced virologic failure or blip, though the proportion of PWH with multiple follow up VLs was low.

Conclusion

Despite a heterogenous population and diverse regimens, most HTE PWH remained on FTR at study end. Most PWH with bVL &lt; 50 remained suppressed and half of PWH with bVL ≥50 achieved suppression over the entire study period. Virologic failure and blips were infrequent, although follow up was limited in this early evaluation of real-world FTR use.

Disclosures

Ricky K. Hsu, MD, Gilead: Honoraria|Merck: Honoraria|ViiV: Advisor/Consultant|ViiV: Grant/Research Support|ViiV: Honoraria Laurence Brunet, PhD, AIDS Healthcare Foundation: Client of my employer|EMD Serono: Client of my employer|Gilead Sciences: Client of my employer|Janssen: Client of my employer|Merck & Co: Client of my employer|TheraTechnologies: Client of my employer|ViiV Healthcare: Client of my employer Jennifer S. Fusco, BS, AIDS Healthcare Foundation: Client of my employer|EMD Serono: Client of my employer|Gilead Sciences: Client of my employer|Janssen: Client of my employer|Merck & Co.: Client of my employer|TheraTechnologies: Client of my employer|ViiV Healthcare: Client of my employer Cassidy Henegar, PhD, MSPH, GlaxoSmithKline: Stocks/Bonds|ViiV Healthcare: full-time employee Vani Vannappagari, MBBS, MPH, PhD, ViiV Healthcare: I am full time employee of ViiV Healthcare and receive GlaxoSmithKline stock as part of my compensation package|ViiV Healthcare: Stocks/Bonds Andrew Clark, MD, ViiV Healthcare: Employee|ViiV Healthcare: Stocks/Bonds Gerald Pierone, Jr., MD, Gilead: Grant/Research Support|GSK-VIIV: Grant/Research Support Gregory P. Fusco, MD, MPH, AIDS Healthcare Foundation: Client of employer|EMD: Grant/Research Support|Gilead Sciences: Client of employer|Janssen: Client of employer|Merck & Co.: Client of employer|Theratechnologies: Client of employer|ViiV Healthcare: Client of employer.

441. Association between Incident HIV-Associated Wasting/Low Weight and All-Cause Mortality in the OPERA® Cohort

Background

HIV-associated wasting (i.e., progressive, involuntary weight loss with both fat and lean tissue loss; HIVAW) is an under-appreciated AIDS-defining illness; the 2012-2018 period prevalence was reported as 18% in a recent claims study in the United States. We aimed to assess the association between incident HIVAW/low weight and all-cause mortality in the era of modern combination antiretroviral therapy (ART).

Methods

In the Observational Pharmaco-Epidemiology Research & Analysis (OPERA®) cohort, PWH without (a) any prior HIVAW/low weight, (b) malignancy within 3 years, and (c) opportunistic infection within 1 year who were active in care between 2016 and 2020 were followed through death, loss to follow-up, or study end (31OCT2021). HIVAW/low weight included a wasting or low BMI/underweight diagnosis (ICD codes, title search) or BMI &lt; 20 kg/m2. Hazard ratios (HR) and 95% confidence intervals (CI) for the association between time-dependent incident HIVAW/low weight (exposure) and all-cause mortality (outcome) were estimated with extended Cox regression models. The adjusted model included age at baseline, race, ethnicity, and time-dependent covariates (log10 viral load, Veterans Aging Cohort Study [VACS] Mortality Index score). Viral load and VACS score were included as surrogate markers for ART use and comorbidities, respectively. Linear and quadratic terms of continuous variables were included.

Results

Of 67,119 PWH without prior HIVAW/low weight in OPERA®, 62,314 (93%) PWH had non-missing covariate data and were included in the models; baseline characteristics did not differ between the full and model study populations (Table 1). Over a median follow-up of 45 months (interquartile range: 27, 65), there were 4,755 (8%) cases of incident HIVAW/low weight and 1,354 (2%) deaths. In the adjusted model, PWH who experienced incident HIVAW/low weight had a significantly increased risk of death over follow-up than those who did not experience HIVAW/low weight (HR: 1.96; 95% CI: 1.68, 2.27) (Table 2).

Conclusion

In this analysis of 62,314 PWH in care, incident HIVAW/low weight was associated with twice the risk for all-cause mortality in the modern ART era. Particular attention needs to be paid to HIVAW/low weight among PWH to restore health and potentially reduce the risk of death.

Disclosures

Rachel P. Weber, PhD, AIDS Healthcare Foundation: Client of my employer|EMD Serono: Client of my employer|Gilead Sciences: Client of my employer|Janssen: Client of my employer|Merck & Co.: Client of my employer|TheraTechnologies: Client of my employer|ViiV Healthcare: Client of my employer Laurence Brunet, PhD, AIDS Healthcare Foundation: Client of my employer|EMD Serono: Client of my employer|Gilead Sciences: Client of my employer|Janssen: Client of my employer|Merck & Co: Client of my employer|TheraTechnologies: Client of my employer|ViiV Healthcare: Client of my employer Javeed Siddiqui, MD, MPH, Abbvie: Advisor/Consultant|Abbvie: Honoraria|Cumberland pharmaceuticals: Advisor/Consultant|Cumberland pharmaceuticals: Honoraria|EMD serono: Advisor/Consultant|EMD serono: Honoraria|Merck: Advisor/Consultant|Merck: Honoraria Javeed Siddiqui, MD, MPH, Abbvie: Advisor/Consultant|Abbvie: Honoraria|Cumberland pharmaceuticals: Advisor/Consultant|Cumberland pharmaceuticals: Honoraria|EMD serono: Advisor/Consultant|EMD serono: Honoraria|Merck: Advisor/Consultant|Merck: Honoraria Michael Harbour, MD, MPH, FACP, EMD Serono: Employee Amy L. Phillips, PharmD, EMD Serono, Inc.: Employment Brooke Hayward, SM, MBA, EMD Serono, Inc.: Employee Jennifer S. Fusco, BS, AIDS Healthcare Foundation: Client of my employer|EMD Serono: Client of my employer|Gilead Sciences: Client of my employer|Janssen: Client of my employer|Merck & Co.: Client of my employer|TheraTechnologies: Client of my employer|ViiV Healthcare: Client of my employer Ricky K. Hsu, MD, Gilead: Honoraria|Merck: Honoraria|ViiV: Advisor/Consultant|ViiV: Grant/Research Support|ViiV: Honoraria Gregory P. Fusco, MD, MPH, AIDS Healthcare Foundation: Client of employer|EMD: Grant/Research Support|Gilead Sciences: Client of employer|Janssen: Client of employer|Merck & Co.: Client of employer|Theratechnologies: Client of employer|ViiV Healthcare: Client of employer.

1582. Real-World Use of Long-Acting Cabotegravir + Rilpivirine in the US: Effectiveness in the First Year

Background

The first long-acting (LA) antiretroviral therapy (ART) regimen, cabotegravir+rilpivirine (CAB+RPV) injection, was approved by the FDA in January 2021 for ART-experienced, people with HIV (PWH) with undetectable viral load (VL< 50 copies/mL). We assessed clinical effectiveness of CAB+RPV LA in the first year of use in the United States (US).

Methods

Using electronic health record data from the OPERA® cohort, all ART-experienced adults who received ≥1 CAB+RPV LA prescriptions for the first time between 21Jan2021 and 28Feb2022 were followed until 13Mar2022. Discontinuation was defined as an ART switch or > 2 consecutive missed doses. VL were monitored from first injection until end of follow-up or discontinuation. Confirmed virologic failure was defined as 2 consecutive VLs > 200 copies/mL or 1 VL > 200 copies/mL + discontinuation. Results were stratified by VL at first prescription (i.e., suppressed: < 200 copies/mL; viremic: ≥ 200 copies/mL).

Results

Of 994 PWH prescribed CAB+RPV, all were ART-experienced and 85% had undetectable VL (< 50 copies/mL), 90% were suppressed (< 200 copies/mL), and the remainder had VL ≥200/mL (6%) or missing baseline VL (4%). Of those prescribed, 344 (38%) received CAB+RPV LA injections over a median 53 (IQR: 35, 79) days; 14% were women, 36% were Black, 29% were Hispanic, 25% had a BMI of ≥30, and the median age was 40 (IQR: 32, 53) years (Table 1). At the end of observation, 62% had not yet received CAB+RPV injections as they were in the process of approval, were on oral lead-in, or had been denied. At study end, 310 (90%) of the 344 remained on CAB+RPV LA with median follow-up of 3.4 (2.2, 6.1) months. Among those with VLs after first injection, the last VL was < 200 copies/mL in 99% and < 50 copies/mL in 94% (Table 2); all follow-up VLs were < 200 copies/mL in 97%, and < 50 copies/mL in 88%. Thirty viremic PWH received CAB+RPV LA injections (Table) with a median VL at first prescription of 4.2 (IQR: 3.2, 4.9) log copies/mL. Five or fewer PWH experienced confirmed virologic failure in each of the suppressed and viremic groups.

Conclusion

In this real-world cohort of PWH who received CAB+RPV LA injections in the US, observations from the first year suggest that this regimen is effective among virologically suppressed individuals.

Disclosures

Michael G. Sension, MD, Gilead: Advisor/Consultant|Gilead: Honoraria|Viiv: Advisor/Consultant|Viiv: Grant/Research Support|Viiv: Honoraria Ricky K. Hsu, MD, Gilead: Honoraria|Merck: Honoraria|ViiV: Advisor/Consultant|ViiV: Grant/Research Support|ViiV: Honoraria Jennifer S. Fusco, BS, AIDS Healthcare Foundation: Client of my employer|EMD Serono: Client of my employer|Gilead Sciences: Client of my employer|Janssen: Client of my employer|Merck & Co.: Client of my employer|TheraTechnologies: Client of my employer|ViiV Healthcare: Client of my employer Laurence Brunet, PhD, AIDS Healthcare Foundation: Client of my employer|EMD Serono: Client of my employer|Gilead Sciences: Client of my employer|Janssen: Client of my employer|Merck & Co: Client of my employer|TheraTechnologies: Client of my employer|ViiV Healthcare: Client of my employer Gayathri Sridhar, MBBS, MPH, PhD, GlaxoSmithKline: Stocks/Bonds|ViiV Healthcare: Employment Vani Vannappagari, MBBS, MPH, PhD, ViiV Healthcare: I am full time employee of ViiV Healthcare and receive GlaxoSmithKline stock as part of my compensation package|ViiV Healthcare: Stocks/Bonds Andrew Zolopa, MD, ViiV Healthcare: full time employee|ViiV Healthcare: Stocks/Bonds Jean A. van Wyk, MB,ChB; MFPM, ViiV Healthcare Limited: I am an employee of ViiV Healthcare|ViiV Healthcare Limited: Stocks/Bonds Gregory P. Fusco, MD, MPH, AIDS Healthcare Foundation: Client of employer|EMD: Grant/Research Support|Gilead Sciences: Client of employer|Janssen: Client of employer|Merck & Co.: Client of employer|Theratechnologies: Client of employer|ViiV Healthcare: Client of employer.

Excessive Weight Gain: Current Antiretroviral Agents in Virologically Suppressed People with HIV

An observational cohort study was conducted with data from the Observational Pharmaco-Epidemiology Research & Analysis (OPERA) cohort to investigate weight gain among virologically suppressed people with HIV (PWH) switching to regimens containing tenofovir alafenamide/emtricitabine/(TAF/FTC). Virologically suppressed, antiretroviral therapy (ART)-experienced PWH switching to TAF/FTC with darunavir/cobicistat (DRV/c), elvitegravir/cobicistat (EVG/c), dolutegravir (DTG), or bictegravir (BIC) were selected. Cox proportional hazards models were used to assess the risk of excessive weight gain (i.e., ≥5% gain within 28 weeks or ≥10% within 54 weeks), by regimen. A linear mixed effects model with random intercept and restricted cubic splines on time was used to assess continuous changes in weight. Confounding was controlled for with both inverse probability of treatment weighting and traditional covariate adjustment. Among 5,536 PWH, 18% gained ≥5% of their weight within 28 weeks, and 9% gained ≥10% within 54 weeks. There were no differences in the risk of excessive weight gain by regimen, although there was a nonstatistically significant 20% increase in the risk of gaining ≥10% within 54 weeks with all regimens compared to DRV/c. Throughout follow-up, the mean predicted weight remained fairly constant, with no notable differentiation between regimens. Expected weight gains ranged from +0.2 to +0.3 kg at 6 months and from +0.5 to +0.6 kg at 24 months. In conclusion, in this study of virologically suppressed, ART-experienced PWH switching to regimens containing TAF/FTC and DRV/c, EVG/c, DTG, or BIC, up to 18% experienced excessive levels of weight gain. However, no statistically significant difference was observed across regimens.

Are We Hitting the Target? HIV Pre-Exposure Prophylaxis from 2012 to 2020 in the OPERA Cohort

Preventing HIV transmission is a crucial step in ending the HIV epidemic. Safe and effective pre-exposure prophylaxis (PrEP) has been available in the United States since 2012. We set out to determine if persons at greatest risk for HIV acquisition were receiving HIV PrEP. HIV-negative individuals from the Observational Pharmaco-Epidemiology Research & Analysis (OPERA) cohort who were prescribed daily PrEP were contrasted with newly diagnosed HIV persons without PrEP use between July 16, 2012 and October 31, 2020 to determine if the PrEP prescriptions reached the populations who were seroconverting. Poisson regression was used to estimate incidence rates of seroconversion to HIV among PrEP initiators, as well as new diagnoses of sexually transmitted infections among both the PrEP group and the newly HIV+ group. Out of the 14,598 PrEP users and 3558 persons newly diagnosed with HIV in OPERA, demographics varied widely. Older individuals, those of non-Black race, men, nonintravenous (IV) drug users, and those with commercial insurance were proportionally overrepresented among those prescribed PrEP compared to persons newly diagnosed with HIV during the same time period. Over 82% of new HIV+ individuals received care in the southern United States compared to only 45% of PrEP users. Seroconversion to HIV among PrEP users was generally uncommon, although more frequent among those who identified as Black individuals, especially in the 13-25 years old age range. In conclusion, providers need innovative programs to better identify, educate, and link those at greatest risk of HIV acquisition, especially young people, women, Black individuals, and IV drug users, to PrEP.

To dose-adjust or not to dose-adjust: lamivudine dose in kidney impairment

OBJECTIVES

To assess the risk of adverse diagnoses and laboratory abnormalities associated with a 300 or 150 mg daily dose of lamivudine (3TC) initiated by people with HIV (PWH) with an estimated glomerular filtration rate (eGFR) between at least 30 and 49 ml/min per 1.73 m2 or less.

DESIGN

Longitudinal study based on electronic health records of 539 PWH with eGFR between at least 30 and 49 ml/min per 1.73 m2 or less from the Observational Pharmaco-Epidemiology Research and Analysis (OPERA) cohort.

METHODS

Common unintended effects of 3TC were evaluated as composite outcomes. We estimated the incidence (univariate Poisson regression) and association between dose and incident composite outcomes (multivariate Poisson regression) among PWH without the relevant diagnoses or laboratory abnormalities at 3TC initiation.

RESULTS

PWH initiating 150 mg 3TC had higher HIV RNA, lower eGFR, and more comorbidities than those initiating 300 mg 3TC. The prevalence of relevant diagnoses and laboratory abnormalities was similar in both groups. The most common lab abnormality was low hemoglobin. There was no statistically significant difference in incident adverse diagnoses/severe lab abnormalities with 300 mg versus 150 mg [incidence rate ratio (IRR): 1.51; 95% confidence interval (CI) 0.59--3.92). However, a statistically significant association was observed when gastrointestinal symptoms/moderate lab abnormalities were included in the outcome (IRR: 3.07, 95% CI 1.12--8.40).

CONCLUSION

As 3TC is a well tolerated drug with a wide therapeutic window, dose adjustment may be unnecessary among PWH with eGFR between at least 30 and 49 ml/min per 1.73 m2 or less. Clinical judgement is key when weighing the risks and benefits of 3TC dose adjustment for PWH experiencing gastrointestinal symptoms or moderate lab abnormalities.

Weight gain before and after switch from TDF to TAF in a U.S. cohort study

Introduction

Although weight gain has been reported with the use of integrase strand transfer inhibitors (InSTI), concurrent use of tenofovir alafenamide (TAF) has been implicated in recent studies. This study examined weight changes in people living with HIV (PLWH) who switched from tenofovir disoproxil fumarate (TDF) to TAF, to clarify the relative contribution to weight gain of core agents versus TDF to TAF switch.

Methods

Antiretroviral‐experienced, virologically suppressed PLWH in the U.S. OPERA cohort were included if they switched from TDF to TAF (5NOV2015‐28FEB2019) and either maintained all other antiretrovirals or switched from a non‐InSTI to an InSTI. Linear mixed models were used to assess weight changes before/after the switch to TAF (restricted cubic splines on time) and rates of change over time (linear splines on time, based on the shape of the weight change curves). Changes in weight on TDF or TAF were assessed among those who maintained other antiretrovirals (overall, by core class), and those who maintained an InSTI or switched to an InSTI (by core agent). All models were adjusted for age, sex, race, (age‐sex, race‐sex interactions), BMI, CD4 cell count, endocrine disorders and concurrent medications that could affect weight.

Results

A total of 6908 PLWH were included, with 5479 maintaining all other antiretrovirals (boosted protease inhibitor: 746, non‐nucleoside reverse transcriptase inhibitor: 1452, InSTI: 3281) and 1429 switching from a non‐InSTI to an InSTI (elvitegravir/cobicistat: 1120, dolutegravir: 174, bictegravir: 129). In adjusted models, modest weight gain was observed over time on TDF for most (0.24 to 0.71 kg/year); raltegravir was the exception with weight loss. Switching to TAF was associated with early, pronounced weight gain for all (1.80 to 4.47 kg/year). This effect with TAF switch was observed both in PLWH maintaining other antiretrovirals and those switching to an InSTI, regardless of which InSTI agent was used. Weight gain tended to slow down or plateau approximately nine months after switch to TAF.

Conclusions

In this large, diverse U.S. cohort of PLWH, switching from TDF to TAF was associated with pronounced weight gain immediately after switch, regardless of the core class or core agent, suggesting an independent effect of TAF on weight gain.

Abacavir Hypersensitivity Reaction Reporting Rates During a Decade of HLA-B*5701 Screening as a Risk-Mitigation Measure

INTRODUCTION

Human leukocyte antigen (HLA)-B*5701 screening identifies patients at increased risk for abacavir (ABC) hypersensitivity reaction (HSR). Screening was adopted in GlaxoSmithKline and ViiV Healthcare clinical trials in 2007 and human immunodeficiency virus treatment guidelines in 2008. Company meta-analyses of trials pre-HLA-B*5701 screening reported HSR rates of 4-8%. We analyzed the effectiveness of HLA-B*5701 screening on reducing HSR rates using clinical trial, Observational Pharmaco-Epidemiology Research & Analysis (OPERA) cohort, and spontaneous reporting data.

METHODS

A meta-analysis examined 12 trials in 3063 HLA-B*5701-negative patients receiving an ABC-containing regimen from April 9, 2007, to September 22, 2015. Potential cases were identified using prespecified Medical Dictionary for Regulatory Activities (MedDRA) preferred terms (drug hypersensitivity, hypersensitivity, anaphylactic reaction, anaphylaxis) and adjudicated against a Company ABC HSR case definition. Investigator-diagnosed cases were identified and rates were calculated. In the OPERA cohort, 9619 patients initiating their first ABC-containing regimen from January 1, 1999, to January 1, 2016, were identified. Patients were observed from regimen start until the earliest-following censoring event: ABC discontinuation, loss to follow-up, death, or study end (July 31, 2016). OPERA physicians evaluated events against OPERA definitions for definite/probable cases of ABC HSR; rates were calculated pre- and post-2008. The Company case definition was used to identify spontaneously reported cases for four marketed ABC-containing products; reporting rates were calculated using estimated exposure from sales data, through December 31, 2016.

RESULTS

Suspected ABC HSR rates were 1.3% or less in the meta-analysis. In the OPERA cohort, the rate was 0.4% among patients initiating ABC post-2008 versus 1.3% pre-2008 (p<0.0001). Spontaneous reporting rates were low post-2008 (54 to 22 cases per 100,000 patient-years exposure [PYE]) versus pre-2008 (618 to 55 cases per 100,000 PYE).

CONCLUSIONS

Clinically suspected ABC HSR rates were 1.3% or less in HLA-B*5701-negative patients. Recognizing their limitations, data from the OPERA cohort and spontaneous reporting indicate that HLA-B*5701 screening has reduced reporting rates of suspected HSR in clinical practice. Where screening for HLA-B*5701 is standard care, patients should be confirmed negative for this allele before starting ABC treatment.

The major genetic determinants of HIV-1 control affect HLA class I peptide presentation

Infectious and inflammatory diseases have repeatedly shown strong genetic associations within the major histocompatibility complex (MHC); however, the basis for these associations remains elusive. To define host genetic effects on the outcome of a chronic viral infection, we performed genome-wide association analysis in a multiethnic cohort of HIV-1 controllers and progressors, and we analyzed the effects of individual amino acids within the classical human leukocyte antigen (HLA) proteins. We identified >300 genome-wide significant single-nucleotide polymorphisms (SNPs) within the MHC and none elsewhere. Specific amino acids in the HLA-B peptide binding groove, as well as an independent HLA-C effect, explain the SNP associations and reconcile both protective and risk HLA alleles. These results implicate the nature of the HLA-viral peptide interaction as the major factor modulating durable control of HIV infection.

Modulation of K65R selection by zidovudine inclusion: analysis of HIV resistance selection in subjects with virologic failure receiving once-daily abacavir/lamivudine/zidovudine and tenofovir DF (study COL40263)

COL40263 was a pilot 48-week, open-label, multicenter study evaluating the efficacy and safety of once-daily coformulated abacavir/lamivudine/zidovudine plus tenofovir in ART-naive, HIV-infected subjects. We examined the patterns of resistance that were selected on-therapy through 48 weeks in subjects with virologic nonresponse (VF). A total of 123 antiretroviral-naive HIV-1-infected subjects with plasma HIV-1 RNA > or = 30,000copies/ml were enrolled. For subjects with confirmed VF (HIV-1 RNA > or = 400 copies/ml at week 24 or later), HIV population genotypic and phenotypic analysis was performed. Of the 123 enrolled subjects, 14 (11%) had confirmed plasma HIV-1 RNA > or = 400 copies/ml through week 48. Of these subjects, 3/14 had evidence of drug resistance at baseline: 2/14 had HIV with K103N, Y188F/H/L/Y, and/or T215A and 1/14 had reduced zidovudine susceptibility. At the last time point analyzed, 4/14 subjects had wild-type HIV, while 10/14 subjects had HIV with either thymidine analogue mutations (TAMS) alone (3/10), TAMS + M184V (4/10), M184V only (1/10), or K65R/K (2/10). Matched phenotype was obtained for 13/14 subjects and 8/13 (62%) subjects had reduced susceptibility to one or more study drugs: 2/13 tenofovir, 3/13 abacavir, 4/13 zidovudine, and 7/13 lamivudine. The resistance pattern in COL40263 subjects with VF differs significantly from that reported for tenofovir-containing triple-nucleoside regimens. TAMs were detected in the majority (7/10) of samples from subjects with VF who selected any resistance mutation. These data suggest that TAMs selection is a preferred resistance route of this combination, with zidovudine modulating the resistance pathway against selection for K65R.

Pancreatitis caused by common bile duct stones in a 3-year-old boy with prior surgery for a choledochal cyst

Pancreatitis in children is uncommon. Compared to adults, pancreatitis in children is usually related to trauma, anatomic anomalies, infections, hereditary, and systemic disease, but not gallstones or alcohol. Most cases do not require endoscopic intervention. We report an unusual case of recurrent pancreatitis in a child related to common bile duct stones requiring endoscopic treatments after surgical treatment for choledochal cyst.

Therapeutic ERCP in the management of pancreatitis in children

BACKGROUND

The use of diagnostic and therapeutic endoscopic retrograde cholangiopancreatography (ERCP) is increasing in the management of pancreatobiliary diseases in children.

METHODS

Over a 32-month period, we performed 34 ERCP procedures for the treatment of pancreatitis in 22 children at two university hospitals. Demographics and clinical data and ERCP findings were documented. Clinical status was assessed 6 months before the first ERCP and 6 months after the last ERCP, according to general condition, severity and frequency of pain, and health care encounters (emergency department visits, clinic visits, and hospital admissions related to the pancreatitis).

RESULTS

Mean age of the patients was 10.7 years (range 1.5 to 17 years). Abdominal pain was the main presenting symptoms with hyperamylasemia and hyperlipasemia. Clinical diagnoses included acute pancreatitis (6), recurrent pancreatitis (5), and chronic pancreatitis (11). The mean follow-up was 16.4 months. Nine patients had sphincter manometry, with abnormal results leading to biliary sphincterotomy in 4. Fifteen patients underwent a total of 23 therapeutic ERCP procedures unrelated to sphincter dysfunction. There were 2 complications of 34 procedures (6%), both being mild pancreatitis after sphincter manometry. There were no deaths. There was a significant reduction in frequency (p < 0.01) and severity of pain (p < 0.01) after intervention. Patients without pancreatographic changes of chronic pancreatitis had the most marked clinical improvement (p < 0.05). In those with ductal changes of chronic pancreatitis, clinical improvement was not predicted by the extent of ductal changes. There was a significant decrease in health care encounters (p < 0.05) and improvement in general condition (p < 0.01) after endoscopic therapy, especially in those with a normal pancreatogram.

CONCLUSIONS

Therapeutic ERCP is safe in pediatric patients with pancreatitis. Significant clinical improvement is achieved in patients with biliary or pancreatic stone disease. Prospective studies with long-term follow-up are needed to determine the impact of endoscopic therapy in patients with chronic pancreatitis and sphincter of Oddi dysfunction.

Crohn's disease in the Chinese population. An experience from Hong Kong

PURPOSE

Crohn's disease was extremely rare among Chinese. We reviewed all cases diagnosed as having Crohn's disease during a five-year period.

METHODS

A diagnosis of Crohn's disease was made only if all of the following criteria were fulfilled: 1) clinical symptom(s) and sign(s) compatible with chronic inflammatory bowel disease; 2) exclusion of intestinal infection by repeated stool cultures; 3) macroscopic features of small and/or large intestinal inflammation with skip lesion, stricture, and fistula formation; 4) histologic features of Crohn's disease, i.e., focal lymphoid aggregate, focal cryptitis, and granuloma formation; 5) clinical response to conventional therapy for inflammatory bowel disease.

RESULTS

Fifteen ethnic Chinese patients were diagnosed as having Crohn's disease in this period. All patients had colitis, whereas small intestine inflammation was documented in only 47 percent of patients. Extraintestinal manifestations were uncommon except for arthropathy: ankylosing spondylitis (2), sacroiliitis (1), juvenile rheumatoid arthritis (1), and colitic arthritis (1). The majority of our patients responded to medical therapy. Surgery was undertaken in 33 percent of patients.

CONCLUSION

Although there is a general increased incidence of Crohn's disease in the Western world, we too are beginning to see more cases in the Far East. Nevertheless, gastrointestinal infection with bacteria and/or parasites should still be carefully excluded in these countries.

A humanized antibody specific for the platelet integrin gpIIb/IIIa

C4G1, a murine mAb reactive with the platelet gpIIb/IIIa integrin, was humanized for potential treatment of thrombosis-related disorders. The variable regions of light- and heavy-chain cDNAs from the C4G1 hybridoma were first cloned and sequenced. Humanized C4G1 Ab of the IgG1 isotype was constructed by combining the complementarity-determining regions of C4G1 with human framework and constant regions. The human framework was chosen to maximize homology with the C4G1 variable region sequence, and a computer model of C4G1 was used to aid design of the final framework sequence. Genetic constructs were also developed to produce Fab and F(ab')2 fragments of the humanized C4G1 Ab. The humanized IgG1 Ab as well as the Fab and F(ab')2 fragments showed equivalent binding affinities to their murine counterparts, indicating no loss in binding affinity during the humanization process. The humanized Ab and its fragments were also shown to inhibit platelet aggregation and to inhibit binding of fibrinogen to gpIIb/IIIa in vitro.

A humanized antibody specific for the platelet integrin gpIIb/IIIa

C4G1, a murine mAb reactive with the platelet gpIIb/IIIa integrin, was humanized for potential treatment of thrombosis-related disorders. The variable regions of light- and heavy-chain cDNAs from the C4G1 hybridoma were first cloned and sequenced. Humanized C4G1 Ab of the IgG1 isotype was constructed by combining the complementarity-determining regions of C4G1 with human framework and constant regions. The human framework was chosen to maximize homology with the C4G1 variable region sequence, and a computer model of C4G1 was used to aid design of the final framework sequence. Genetic constructs were also developed to produce Fab and F(ab')2 fragments of the humanized C4G1 Ab. The humanized IgG1 Ab as well as the Fab and F(ab')2 fragments showed equivalent binding affinities to their murine counterparts, indicating no loss in binding affinity during the humanization process. The humanized Ab and its fragments were also shown to inhibit platelet aggregation and to inhibit binding of fibrinogen to gpIIb/IIIa in vitro.

The RRE of human immunodeficiency virus type 1 contributes to cell-type-specific viral tropism

As part of a general program investigating the mechanism of the Rev axis of human immunodeficiency virus type 1 (HIV-1) autoregulation, a series of proviral HIV-1 mutants which differ from the parental HXB2 strain at selected positions within the RRE were constructed. All of the mutations were designed to perturb the RRE by introducing local helix disruptions without altering the coding potential of the overlapping envelope open reading frame. Viral replication in various cell types was monitored by a cell supernatant reverse transcriptase assay and Northern (RNA blot) analysis. All proviral RRE mutants displayed at least some impairment in replication. However, the relative impairment varied drastically among the various cell types tested. This suggests that the RRE may contribute to cell-type-specific viral tropism.

Genomic heterogeneity of DNA repair. Role in aging?

The introduction and repair of DNA lesions are generally heterogeneous with respect to different genomic domains. In particular, the repair of helix-distorting damage, such as the cyclobutane pyrimidine dimers (CPD) induced by ultraviolet light occurs selectively in expressed genes. This is due in large part to the preferential repair of transcribed DNA strands, which is then reflected in a bias toward mutagenesis from persisting lesions in nontranscribed strands. Consequently, determination of overall genomic repair efficiencies may not be a good indicator of cellular sensitivity to agents that damage DNA. Although some studies suggest an age-related accumulation of altered nucleotides in DNA, we do not know the intragenomic distribution of those changes and whether they are relevant to the physiological aspects of aging. Subtle changes in the pattern of preferential repair during maturation could have profound effects on cell and tissue function. DNA repair has been analyzed in differentiating cell systems as possible models for aging. We have observed attenuated overall repair of CPD in differentiated rat myoblasts or PC12 neuron-like cells. In both model systems, several expressed genes have been shown to be repaired relatively efficiently but without strand specificity. In another model system of human HT1080 fibroblasts differentiating in the presence of dexamethasone, we demonstrated enhanced repair in the gene for plasminogen activator inhibitor I whose transcription is induced and, correspondingly, a reduced repair rate in the urokinase plasminogen activator gene whose transcription is suppressed. We conclude that any attempted correlation of the phenomena of aging with DNA repair should focus on the relevant genes in the tissue of interest.