Escape and lipodystrophy in acromegaly during pegvisomant therapy, a retrospective multicentre Spanish study

Efficacy and Safety of Pegvisomant in the Treatment of Acromegaly

Pegvisomant, the first and currently only clinically available growth hormone receptor antagonist, is an effective therapeutic option for the medical treatment of acromegaly, a rare disorder characterized by excessive growth hormone secretion. With now over 20 years of real world experience, its safety and efficacy is well-established. However, several aspects of its clinical use are still controversially discussed. The high cost of pegvisomant has limited its use in several countries, and recent studies have reported a lower efficacy than the initial clinical trials. A reported increase in tumor volume under therapy varies between studies and has been attributed to either actual growth or re-expansion after cessation of somatostatin receptor ligand therapy. Furthermore, different combinations of pegvisomant and other therapeutic agents aiming at reduction of acromegaly disease activity have been proposed to increase or retain effectiveness while lowering side effects and cost. This review aims to assess current clinical data on the safety and efficacy of pegvisomant while also addressing controversies surrounding its use.

The p300 Inhibitor A-485 Exerts Antitumor Activity in Growth Hormone Pituitary Adenoma

CONTEXT

Growth hormone pituitary adenoma (GHPA), a major subtype of pituitary adenoma (PA), can lead to progressive somatic disfigurement, multiple complications, and even increased mortality. The efficacy of current treatments is limited; thus, a novel pharmacological treatment is urgently needed. As a histone acetyltransferase (HAT) coactivator, p300 can regulate the transcription of several genes that are crucial for PA tumorigenesis and progression. However, the role of p300 and its catalytic inhibitor in GHPA is still unclear.

OBJECTIVE

We aimed to identify the expression of p300 in GHPA and in normal pituitary glands.

METHODS

The expression of p300 was detected in GHPA and normal pituitary tissues. Genetic knockdown was performed by siRNA. The efficacy of the p300 inhibitor A-485 in the cell cycle, proliferation, apoptosis, and hormone secretion was investigated by flow cytometry, ELISAs, Western blotting, and qRT-PCR. RNA sequencing, bioinformatic analysis, and subsequent validation experiments were performed to reveal the potential biological mechanism of A-485.

RESULTS

High expression of p300 was found in GHPA tissues compared with normal pituitary tissues. Knockdown of p300 inhibited cell proliferation and clone formation. Treatment with A-485 suppressed cell growth and inhibited the secretion of GH in vitro and in vivo. Further mechanistic studies showed that A-485 could downregulate the expression or activity of several oncogenes, such as genes in the Pttg1, c-Myc, cAMP and PI3K/AKT/mTOR signaling pathways, which are crucial for PA tumorigenesis and progression.

CONCLUSION

Our findings demonstrate that inhibition of HAT p300 by its selective inhibitor A-485 is a promising therapy for GHPA.

Pegvisomant in the treatment of acromegaly

Despite improvements in surgical techniques, current radiotherapy options and development of long-acting somatostatin analogues, biochemical control of acromegaly is not achieved in some patients. The failure to achieve optimal serum growth hormone (RH) and insulin-like growth factor-1 (IGF-1) levels means increased morbidity and mortality of acromegaly patients. The RH receptor antagonist pegvisomant (PEG) is a genetically engineered RH analog that prevents of RH receptor dimerization, i.e. a process that is crucial for the action of RH at the cellular level. The effect of the treatment is suppression of IGF-1 production. In pilot studies, normalization of IGF-1 levels was achieved in up to 90 % of patients receiving PEG. However, PEG efficacy in clinical settings is slightly lower (65 to 97 %) than reported in the key studies. A rare side effect of treatment is elevations of liver transaminases. In addition, pituitary tumor growth progression has been reported in several cases. In this review article, we present long-term data on pegvisomant treatment and discuss its associated risks and benefits.

More than a decade of real-world experience of pegvisomant for acromegaly: ACROSTUDY

OBJECTIVE

To report the final long-term safety and efficacy analyses of patients with acromegaly treated with pegvisomant from the ACROSTUDY.

DESIGN

Global (15 countries), multicentre, non-interventional study (2004-2017).

METHODS

The complete ACROSTUDY cohort comprised patients with acromegaly, who were being treated with pegvisomant (PEGV) prior to the study or at enrolment. The main endpoints were long-term safety (comorbidities, adverse events (AEs), pituitary tumour volumes, liver tests) and efficacy (IGF1 changes).

RESULTS

Patients (n = 2221) were treated with PEGV for a median of 9.3 years (range, 0-20.8 years) and followed up for a median of 7.4 years (range, 0-13.9 years). Before PEGV, 96.3% had received other acromegaly treatments (surgery/radiotherapy/medications). Before PEGV treatment, 87.2% of patients reported comorbidities. During ACROSTUDY, 5567 AEs were reported in 56.5% of patients and of these 613 were considered treatment-related (in 16.5% of patients) and led to drug withdrawal in 1.3%. Pituitary imaging showed a tumour size increase in 7.1% of patients; the majority (71.1%) reported no changes. Abnormal AST or ALT liver tests occurred in 3.2% of patients. IGF1 normalization rate improved over time, increasing from 11.4% at PEGV start to 53.7% at year 1, and reaching 75.4% at year 10 with the use of ≥30 mg PEGV/day in an increasing proportion of patients.

CONCLUSION

This comprehensive review of the complete cohort in ACROSTUDY confirmed the overall favourable benefit-to-risk profile and high efficacy of PEGV as mono- and combination therapy in patients with an aggressive course/uncontrolled/active acromegaly requiring long-term medical therapy for control.

Pegvisomant in combination or pegvisomant alone after failure of somatostatin analogs in acromegaly patients: an observational French ACROSTUDY cohort study

OBJECTIVE

After surgery, when somatostatin analogs (SAs) do not normalise IGF-I, pegvisomant (PEG) is indicated. Our aim was to define the medical reasons for the treatment of patients with PEG as monotherapy (M) or combined with SA, either as primary bitherapy, PB (PEG is secondarily introduced after SA) or as secondary bitherapy, SB (SAs secondarily introduced after PEG).

METHODS

We retrospectively analysed French data from ACROSTUDY.

RESULTS

167, 88 and 57 patients were treated with M, PB or SB, respectively, during a median time of 80, 42 and 70 months. The median PEG dose was respectively 15, 10 and 20 mg. Before PEG, the mean IGF-I level did not differ between M and PB but the proportion of patients with suprasellar tumour extension was higher in PB group (67.5% vs. 44.4%, P = 0.022). SB regimen was used preferentially in patients with tumour increase and IGF-I level difficult to normalise under PEG. In both secondary regimens, the decrease of the frequency of PEG's injections, compared to monotherapy was confirmed. However, the mean weekly dose of PEG between M and PB remained the same.

CONCLUSIONS

The medical rationale for continuing SAs rather than switching to PEG alone in patients who do not normalise IGF-I under SAs was a tumour concern with suprasellar extension and tumour shrinkage under SA. A potential explanation for introducing SA in association with PEG appears to be a tumour enlargement and difficulties to normalise IGF-I levels under PEG given alone. In both regimens, the prospect of lowering PEG injection frequency favoured the choice.

COMPARATIVE EFFICACY OF MEDICAL TREATMENT FOR ACROMEGALY: A SYSTEMATIC REVIEW AND NETWORK META-ANALYSIS OF INTEGRATED RANDOMIZED TRIALS AND OBSERVATIONAL STUDIES

Objective: Comprehensive evidence comparing different medications for acromegaly is scarce. The aim of this study was to perform a network meta-analysis based on evidence from both randomized trials and observational studies of medical treatments for acromegaly. Methods: Electronic databases were searched for both observational studies and randomized trials that enrolled acromegaly patients treated with medications of interest. Simulated trials were generated by a machine learning algorithm and then synthesized with Bayesian random-effects network meta-analyses. The main outcome was the rate of insulin-like growth factor 1 (IGF-1) control after medical treatment. Results: We included 90 studies (100 arms, 4,523 patients) before matching. After matching, 28 simulated trials were generated. Balance of matched arms was checked by spatial distance and correlation matrix. Cotreatment with somatostatin receptor ligands and pegvisomant was the most effective treatment compared with other treatments. In unselected patients, pegvisomant was better than octreotide long-acting release (logOR, 0.85; 95% credible interval [CrI], 0.05 to 1.65) or lanreotide (logOR, 1.09, 95% CrI, 0.05 to 2.14), and the mean absolute IGF-1 control rate ranged from 40 to 60%. In partially responsive patients, cotreatment with somatostatin receptor ligands and pegvisomant was similar to pegvisomant monotherapy, ranking as the most two effective treatments, and the mean absolute IGF-1 control rate was over 60%. Conclusion: Our analysis suggested that the combination of data from observational studies and randomized trials in network meta-analysis was feasible. The findings of this network meta-analysis provided robust evidence supporting the current guidelines in treatment strategy for acromegaly. Abbreviations: CrI = credible interval; DA = dopamine agonist; GH = growth hormone; IGF-1 = insulin-like growth factor 1; ITT = intention-to-treat; LAN = lanreotide; LAN-ATG = lanreotide autogel; OCT = octreotide; OCT-LAR = octreotide long acting repeatable; OR = odds ratio; PEG = pegvisomant; PP = per-protocol; SRL = somatostatin receptor ligand.

Effectiveness and safety of pegvisomant: a systematic review and meta-analysis of observational longitudinal studies

PURPOSE

Acromegaly is a rare disease that often requires drug treatment to achieve control, with pegvisomant being one of the most widely used therapies. In the present paper, we aimed to obtain evidence regarding the effectiveness and safety of pegvisomant by reviewing real-world observational longitudinal studies.

METHODS

A systematic review was performed with a meta-analysis of event rates (95% confidence interval (CI)) using a random effects model. Sensitivity and subgroup analyses were performed (comprehensive meta-analysis 2.0). The systematic review was performed in accordance to preferred reporting items for systematic reviews and meta-analyses, meta-analysis of observational studies in epidemiology, and Cochrane recommendations (PROSPERO register CRD 42017059880). PubMed, Scopus, Web of Science, and SciELO were used to search for literature. Observational studies in patients using pegvisomant for the treatment of acromegaly were included.

RESULTS

Initially, 552 papers were retrieved from the databases; and 31 articles were included in the qualitative analysis and 14 in the quantitative analysis. Eight primary meta-analyses were performed. The overall rate of patients with disease control was of 60.9% (51.8-69.3%; 95% CI). When considering patients under monotherapy, the control rate was 71.7% (64.0-78.4%; 95% CI). Tumor growth was estimated in 7.3% (4.7-11.1%; 95% CI) and elevation of transaminases in 3.0% (1.7-5.2%; 95% CI).

CONCLUSIONS

The real-world data showed that the effectiveness of pegvisomant is not as high as reported in interventional studies. Acromegaly appears to be better controlled when pegvisomant is used as a monotherapy. No serious adverse events were associated with the use of pegvisomant; however, given the high cost of this drug, further studies are required.

Pegvisomant in acromegaly: an update

BACKGROUND

In 2007, we published an opinion document to review the role of pegvisomant (PEG) in the treatment of acromegaly. Since then, new evidence emerged on the biochemical and clinical effects of PEG and on its long-term efficacy and safety.

AIM

We here reviewed the emerging aspects of the use of PEG in clinical practice in the light of the most recent literature.

RESULTS

The clinical use of PEG is still suboptimal, considering that it remains the most powerful tool to control IGF-I in acromegaly allowing to obtain, with a pharmacological treatment, the most important clinical effects in terms of signs and symptoms, quality of life and comorbidities. The number of patients with acromegaly exposed to PEG worldwide has become quite elevated and the prolonged follow-up allows now to deal quite satisfactorily with many clinical issues including major safety issues, such as the concerns about possible tumour (re)growth under PEG. The positive or neutral impact of PEG on glucose metabolism has been highlighted, and the clinical experience, although limited, with sleep apnoea and pregnancy has been reviewed. Finally, the current concept of somatostatin receptor ligands (SRL) resistance has been addressed, in order to better define the acromegaly patients to whom the PEG option may be offered.

CONCLUSIONS

PEG increasingly appears to be an effective and safe medical option for many patients not controlled by SRL but its use still needs to be optimized.

The chronic syndromes after previous treatment of pituitary tumours

Ultimately, almost all patients who are appropriately treated for pituitary tumours enter a chronic phase with control or cure of hormonal excess, adequate treatment of pituitary insufficiency and relief of mass effects. This phase is associated with improvement of initial signs and symptoms, but also with the persistent consequences of the initial disease and associated treatments. Pituitary insufficiency is a common denominator in many of these patients, and is associated with a reduction in quality of life, despite adequate endocrine substitution. Hypothalamic dysfunction can be present in patients previously treated for visual impairments caused by large suprasellar adenomas, or craniopharyngiomas. In addition to hypopituitarism, these patients can have multisystem morbidities caused by altered hypothalamic function, including weight gain and disturbed regulation of sleep-wake cycles. Mortality can also be affected. Patients cured of Cushing disease or acromegaly have chronic multisystem morbidities (in the case of Cushing disease, also affecting mortality) caused by irreversible effects of the previous excesses of cortisol in Cushing disease and growth hormone and insulin-like growth factor 1 in acromegaly. In addition to early diagnosis and treatment of pituitary tumours, research should focus on the amenability of these chronic post-treatment syndromes to therapeutic intervention, to improve quality of life and clinical outcomes.

Update on the use of oral octreotide therapy for acromegaly

Somatostatin analogs are most commonly used in pharmacological treatment of acromegaly. Pegvisomant and dopamine agonists are alternatives, which are used to a lesser extent. Dopamine agonists are the only orally applicable medication but are less effective than the other options. For a large number of patients, life-long pharmacotherapy has to be applied and frequent injections represent a reduction of quality of life for many of them. Areas covered: Recently published evidence for the use of oral octreotide therapy for acromegaly. Expert commentary: Oral octreotide is a novel and effective treatment for acromegaly and the side effects have been shown to be comparable to the injectable SSAs. The combination with a transient permeability enhancer allows intestinal permeation but also enables molecules with a size <70 kDa to pass transiently. This does not seem to have an acute or subacute consequence, but the long-term effect is still elusive. Therefore, more long-term trials are desirable.

Combined treatment of somatostatin analogues with pegvisomant in acromegaly

Treatment of acromegaly with monotherapy long-acting somatostatin analogues (LA-SSA) as primary treatment or after neurosurgery can only achieve complete normalization of insulin-like growth factor I (IGF-I) in roughly 40 % of patients. Recently, one of the acromegaly consensus groups has recommended switching to combined treatment of LA-SSA and pegvisomant (PEGV) in patients with partial response to LA-SSAs. This combination of LA-SSA and PEGV, a growth hormone receptor antagonist, can normalize IGF-I levels in virtually all patients, requiring that the adequate dose of PEGV is used. The required PEGV dose varies significantly between individual acromegaly patients. One of the advantages of the combination therapy is that tumor size control or even tumor shrinkage can be observed in a vast majority of patients. The main side effects of the combination treatment are gastrointestinal symptoms, lipohypertrophy and transient elevated liver transaminases. In this review we provide an overview of the efficacy and safety of the combined treatment of LA-SSAs with PEGV.

Long-term treatment with pegvisomant for acromegaly: a 10-year experience

BACKGROUND

Efficacy of the GH-receptor antagonist pegvisomant (PEG) has differed between preclinical and observational studies mainly due to dose adjustment and IGF-I normalization criteria. An escape phenomenon has also been described, but its definition and underlying causes have not been fully established.

OBJECTIVE

To re-evaluate the outcomes of long-term PEG in a series of previously published patients and analyse the escape phenomenon.

METHODS

We reviewed all patients with acromegaly resistant to SSA in whom PEG was started as monotherapy, who had been included in a previous publication. We prospectively evaluated 64 (56·3% women) from six tertiary care referral hospitals in Spain, for whom data as of June 2014 were available. Escape to PEG was defined as confirmed loss of biochemical control (IGF-I >1·2xULN), after at least 6 months of previous control with a stable dose of PEG.

RESULTS

Patients were followed up for 13·0 (5·9-34·8) years since diagnosis, and 9·0 (4·1-10·4) years since the first administration of PEG. Fifty-one (89·5%) patients had an adequate IGF-I control at the last follow-up visit, 9 of them without treatment. Tumour growth was reported in 6 of 64 cases (9·4%), none of whom had received prior radiotherapy (P = 0·011). Seven patients died during follow-up. We found 16 escapes in 10 patients (15·6%). We identified potential underlying causes in 9 cases (tumour regrowth, previous treatment modifications, concomitant menopause and change in testosterone administration). The reason was unknown in 7 escapes, which occurred in 6 patients (9·4%). All patients, except one, achieved subsequent biochemical control after treatment adjustment.

CONCLUSIONS

We reassure the efficacy and safety of long-term PEG. An escape phenomenon may occur, but it can be overcome by adjusting therapy.

Pegvisomant Treatment in Acromegaly

Historically, medical treatment of acromegaly has mainly been used as an adjuvant therapy after surgery. In the last decades, an increased range of medical therapy options has been available. Somatostatin analogues have become the cornerstones of medical treatment in acromegaly and are even seen as a primary treatment in a selected group of acromegaly patients. The most recent medical treatment available for acromegaly patients is pegvisomant, a growth hormone receptor antagonist. To date, it is the most effective medical treatment, but it is costly. Pegvisomant is used as monotherapy and combined with somatostatin analogues. In this article, we review clinical studies and cohorts that have documented the efficacy of pegvisomant monotherapy and combined therapy and give a concise overview of associated side effects.

Does pegvisomant treatment expertise improve control of resistant acromegaly? The Italian ACROSTUDY experience

OBJECTIVE

GH receptor antagonist pegvisomant is indicated for treatment of patients with resistant acromegaly. We compared safety and treatment outcomes of pegvisomant therapy in patients managed by Italian centers enrolling less or more than 15 cases in ACROSTUDY, a safety surveillance study of long-term pegvisomant treatment of patients with acromegaly. A noninterventional safety surveillance study in which safety and treatment outcomes of pegvisomant were evaluated on the basis of data collected during a 7-year period.

METHODS

A total of 204 acromegaly patients treated by seven centers enrolling 16-49 patients each (group A) and 137 subjects by 18 centers following 3-14 cases ( group B).

RESULTS

Patients of group A and B were treated for 4.4 ± 2.7 and 4.2 ± 2.2 years, respectively. IGF-1 ULN normalized in 64.4 % (n = 56) and 54.4 % (n = 31) in group A and B, respectively, after 1-year treatment, and in 57.3 % (n = 106) and 72.5 % (n = 87) at last visit. Starting doses were significantly higher in group A. They were progressively increased during treatment in both groups, but were higher in uncontrolled patients than in controlled ones only in group A. Reported adverse events were more frequent, and the prevalence of patients with adverse events was higher in group B.

CONCLUSIONS

On the basis of this original study approach, we could speculate that in the centers in which more patients are treated with pegvisomant, less adverse events are reported, but the long-term effectiveness is lower than in centers with less cases, perhaps because of an inadequate patient's selection.