PTH Analogs Research Articles

8410 Lipid modification enhances the calcemic and bone building effects of injected PTH(1-14) and PTH(1-11) fragment peptides in mice

Abstract Disclosure: J. Höppner: None. H. Noda: None. A. Khatri: None. H. Jüppner: None. T.J. Gardella: None. PTH analogs with improved actions in vivo are of interest as potential treatment options for bone and mineral ion diseases such as hypoparathyroidism and osteoporosis. The efficacies in vivo of conventional PTH peptides are generally limited by rapid rates of clearance from the circulation (t1/2 = ∼ 5-30 minutes) and relatively short-dwell times on the receptor (PTH1R). This is especially true for small fragment analogs, such as M (modified)-PTH(1-14), and M-PTH(1-11), which have only been shown to be active in vitro. We explored whether PTH fragment peptide efficacy in vivo could be enhanced by addition of a lipid chain (e.g., a C15 palmitoyl chain (palm)) to either the peptide C-terminus or to the side chain of the amino acid residue at position 11 or 13. The C-tail lipid modifications were specifically designed to promote binding to serum albumin, and hence extend circulation half-life, while the lipid chains at sidechains of residue positions 11 and 13 were designed, based on structural models, to anchor the ligand to the receptor in situ -- i.e. by projection of the acyl chain between two adjacent transmembrane helices and into the surrounding plasma membrane -- to thereby extend receptor dwell time. Assessment of cAMP signaling potencies in HEK293/hPTH1R/glosensor cells revealed that both types of lipid modifications can preserve agonist potency, and that the lipid extensions at position 11 or 13 can indeed prolong receptor dwell times, as shown by extended durations of cAMP signaling after initial binding of Palm 11 or 13-modified M-PTH(1-14) and M-PTH(1-11) peptide fragment. Single subcutaneous injection of either Palm-13-M-PTH(1-14) or Palm-11-M-PTH(1-11) into mice resulted in prolonged increases in blood serum calcium levels, while 14 days of daily injection resulted in profound increases in bone mass, as measured by uCT, and marked increases in blood levels of the bone turnover markers CTX1 and P1NP, whereas non-lipidated M-PTH(1-14) control peptides were inactive in vivo. Peptide lipidation thus holds promise as a strategy to employ in the design of new PTH analogs with improved efficacies in vivo. Presentation: 6/1/2024

7867 Treatment-Related Changes in Total Hip Bone Mineral Density and Fracture Risk Reduction for Drugs With Different Mechanisms of Action: The FNIH-ASBMR-SABRE Project

Abstract Disclosure: T. Vilaca: None. M.T. Schini: None. A.R. Thompson: None. E. Vittinghoff: None. L. Lui: None. S.K. Ewing: None. D.C. Bauer: None. D.M. Black: None. M. Bouxsein: None. R. Eastell: Consulting Fee; Self; Immunodiagnostic Systems, CL Bio, CureTeQ, Biocon, Takeda, UCB. Grant Recipient; Self; Alexion Pharmaceuticals, Inc., Osteolabs. Speaker; Self; Pharmacosmos, Alexion Pharmaceuticals, Inc., Amgen Inc, UCB. Introduction: To date, trials of new anti-osteoporosis therapies have used fractures as primary endpoints. In the FNIH-ASBMR-SABRE project, we posited that the treatment-related change in total hip BMD (THBMD) could be used as a surrogate endpoint for fractures in future clinical trials of new osteoporosis therapies. To demonstrate this, we compiled a large dataset of individual patient data (IPD) from randomized trials and showed a strong association between the change in THBMD at 24 months and reduction in fracture risk. To further explore the use of THBMD as a surrogate endpoint, here we examine whether the association is robust across drugs with different mechanisms of action. Methods: We used IDP (n>120,000 participants) from 22 randomized, placebo-controlled, double-blind trials of osteoporosis medications (17 anti-resorptive, 3 PTH analogs, 1 odanacatib, and 1 romosozumab). We calculated the treatment-related difference (active-placebo) in mean % change in THBMD at 12, 18, and 24 months for each trial. We determined the treatment-related fracture risk reductions for the entire follow-up period, using logistic regression for radiologic vertebral fractures and Cox regression for all clinical fractures (a combination of non-vertebral and clinical vertebral fractures). We used meta-regression to estimate the study-level association (r2) between treatment-related differences in THBMD changes and fracture risk reduction, including only the 17 trials of anti-resorptive drugs and then using the entire set of 22 trials. Since there were only 3 trials of anabolic drugs, we did not perform separate analyses for the anabolic trials. Results: The r2 values were similar between all trials and antiresorptive trials only for both fracture outcomes at all time points. Specifically, for vertebral fractures, the r2 was 0.59 vs 0.70 at 12 mo, 0.69 vs 0.74 at 18 mo, and 0.73 vs 0.78 at 24 mo for all trials vs anti-resorptive trials only. For all clinical fractures, the r2 was 0.46 vs 0.51 at 12 mo, 0.64 vs 0.60 at 18 mo, and 0.71 vs 0.65 at 24 mo for all trials vs anti-resorptive trials only. Conclusion: These results demonstrate that the associations between treatment-related changes in THBMD and fracture risk reductions are robust across anti-osteoporosis therapies with varying mechanisms of action. We conclude that the treatment-related difference in THBMD change would predict fracture reduction equally well for drugs with different mechanisms of action. Presentation: 6/2/2024

8387 PTH Analogs in the Management of Osteoporosis in Patients with HIV: An Under-Investigated Treatment Option

8387 PTH Analogs in the Management of Osteoporosis in Patients with HIV: An Under-Investigated Treatment Option

Stimulation of fracture mineralization by salt-inducible kinase inhibitors.

Over 6.8 million fractures occur annually in the US, with 10% experiencing delayed- or non-union. Anabolic therapeutics like PTH analogs stimulate fracture repair, and small molecule salt inducible kinase (SIK) inhibitors mimic PTH action. This study tests whether the SIK inhibitor YKL-05-099 accelerates fracture callus osteogenesis. 126 female mice underwent femoral shaft pinning and midshaft fracture, receiving daily injections of PBS, YKL-05-099, or PTH. Callus tissues were analyzed via RT-qPCR, histology, single-cell RNA-seq, and μCT imaging. Biomechanical testing evaluated tissue rigidity. A hydrogel-based delivery system for PTH and siRNAs targeting SIK2/SIK3 was developed and tested. YKL-05-099 and PTH-treated mice showed higher mineralized callus volume fraction and improved structural rigidity. RNA-seq indicated YKL-05-099 increased osteoblast subsets and reduced chondrocyte precursors. Hydrogel-released siRNAs maintained target knockdown, accelerating callus mineralization. YKL-05-099 enhances fracture repair, supporting selective SIK inhibitors' development for clinical use. Hydrogel-based siRNA delivery offers targeted localized treatment at fracture sites.

Cardiovascular Safety of Romosozumab vs. PTH Analogs for Osteoporosis Treatment: a Propensity Score Matched Cohort Study.

Romosozumab, a monoclonal sclerostin antibody, is a recently approved highly potent anti-osteoporotic agent with osteoanabolic properties. Clinical use of Romosozumab is hindered by the fear of adverse cardiovascular (CV) events raised following the pivotal ARCH-trial. To assess real-world CV safety of romosozumab vs. alternative osteoanabolic therapies used for treatment of severe osteoporosis. Data was obtained from TriNetX, a global federated health research network including real-time electronic medical records from 113 healthcare organizations with a total of 136,460,930 patients across 16 countries at time of analysis. Inclusion criteria were age ≥ 40 years, a diagnosis of osteoporosis and prescription of romosozumab or a PTH analog (teriparatide/abaloparatide) during 8.2019-8.2022. 1:1 propensity score matched cohorts were created using demographic variables, comorbidities, and medications. Kaplan-Meier analysis was used to estimate the probability of the outcomes. Incident 3-point major adverse CV event or death (3P-MACE) during 1-year of follow-up after the initial prescription. 5,626 and 15,986 patients met the criteria for romosozumab and PTH analog cohorts, respectively, with 5,610 patients per group following propensity score matching. 3P-MACE was significantly less frequent in the romosozumab vs. PTH analog cohort (158 vs 211 patients with an outcome, p=0.003) with reductions in the individual components of the composite outcome: myocardial ischemic events (31 vs 58, p=0.003); cerebrovascular events 56 vs 79, p=0.037; deaths (83 vs 104, p=0.099). In a diverse real-world setting, prescription of romosozumab for osteoporosis is associated with less adverse CV events when compared to PTH analog therapy.

THU470 Blood - Bone Connection? A Case Of A Young Woman With Bilateral Hip Osteonecrosis And Prothrombin Mutation

Abstract Disclosure: A. Sliwinska: None. C. Vanek: None. Introduction: Osteonecrosis of the femoral head (ONFH) is a localized bone disease responsible for 10% of total hip replacements in the United States. Although the condition is a separate entity from osteoporosis, it may co-occur representing underlying systemic bone disease. Many risk factors (steroids, trauma, infections, thrombophilia, blood cell dyscrasias) can predispose to ONFH, therefore, diligent evaluation is required to reveal the underlying cause. There are no FDA approved therapies. Here, we present a case of young woman with bilateral osteonecrosis of femoral head who was found to have prothrombin gene mutation, severe osteoporosis, and was successfully treated with PTH analog therapy with abaloparatide. Case Description: 33-year-old Asian female with no past medical history presented to the Endocrinology clinic for a metabolic bone disease assessment. Two years prior, she developed progressive bilateral hip pain which prompted radiographic evaluation, discovering bilateral ONFH. She was managed non-surgically with a 6-month trial of oral alendronate. Worsening pain prompted left hip decompression surgery with stem cell transfer. Patient had no history of fragility fractures nor family history of bone disease. A bone density revealed Z scores of -3.9 and -3.5 in lumbar spine and total hip, respectively. She was taking 2000 IU vitamin D3 and 600 mg of elemental calcium daily. Her blood tests revealed normal basic metabolic panel, normal complete blood count and liver function tests. Calcium was 9.0 mg/dl (ref:8.6-10.2), albumin 4.6 mg/dl (3.5-4.7 mg/dl), phosphorus 4.0 mg/dl (2.4-4.7 mg/dl), PTH of 28 pg/ml (18-88 pg/ml), Vitamin D 25-hydroxy 41.3 ng/ml (30-80 ng/ml), and TSH was 1.66 mIU/L (0.39-4.17 mIU/L). Patient had an infectious, metabolic and rheumatological work-up that was negative. A thrombosis workup showed a heterozygous prothrombin gene (G20210A) mutation. Factor V Leiden mutation was negative. Repeat Hip MRI showed progression of her ONFH with marked bone marrow edema in femoral head bilaterally. Patient was then started on abaloparatide. After 6 months, hip MRI showed marked improvement with no bone marrow edema. Discussion: Osteonecrosis of the femoral head is a complex disease that can affect young individuals. Bilateral ONFH suggests systemic disease and a thorough work-up is necessary. Although the exact mechanism is unclear, it has been hypothesized that thrombin plays a role in bone homeostasis therefore hematologic disorders may predispose patients to both ONFH and osteoporosis. Medical treatment of ONFH, including bisphosphonates, statins, or anticoagulants, have been suggested. Recently the PTH analog, teriparatide, has shown promising results and found to be beneficial in treating osteonecrosis. Our case highlights importance of thorough work-up for patients with bilateral ONFH and successful use of anabolic agent in this population. Presentation: Thursday, June 15, 2023

THU456 Beyond Guidelines: Treatment Of Concurrent Osteogenesis Imperfecta And Metastatic Bone Disease

Abstract Disclosure: M. Kanin: None. M. Lechner: None. Introduction: Osteogenesis imperfecta (OI) is a rare inherited skeletal dysplasia characterized by bone fragility and skeletal malformation predisposing patients to multiple, recurrent fractures. Treatment of OI is challenging and requires a multidisciplinary approach with emphasis on physical therapy and exercise in addition to medications. There is limited guidance on treatment in adults given truncated life expectancy. Furthermore, guidance on the treatment of OI in the setting of cancer bone metastases is lacking. We present the unique case of a woman with OI and new fracture in the setting of bone-metastatic endometrial cancer. Clinical Case: A 70 year old woman with Type I OI and endometrial adenocarcinoma initially presented to clinic with left hip and groin pain. Prior OI therapy included at least 10 years of bisphosphonate therapy and 3 years of intranasal calcitonin in her fifties. CT imaging revealed a lytic lesion in the L inferior pubic ramus with an associated pathologic fracture. She was treated with denosumab 120mg s.c. every 3 months for six total doses and palliative radiation to the pubic ramus. She developed osteonecrosis of the jaw and further treatment was terminated. She represented 2 years later with right hip pain and was found to have cancer involvement of her right iliac bone. Labs showed creatinine of 0.48 mg/dL, Calcium 9.8 mg/dl, bone specific alkaline phosphatase 17.9ug/L (7.0-22.4 ug/L), n-telopeptide 18.6 nM BCE (6.2-19.0 nM BCE), and vitamin D-25 48ng/ml. DEXA scan showed T scores at the AP spine of -3.2, LFN of -2.1, and RFN of -2.5. Our patient had a high functional status, minimal pain and acceptable quality of life. Given the presence of active bone metastases, we favored treatment with zolendronic acid 4mg i.v. monthly given her high fracture risk, combined with continued cancer therapy targeted to bone metastases. Clinical Lesson: To our knowledge, there are no guidelines or case reports for optimal treatment of patients with concurrent OI and bone metastases. While bisphosphonates are typically a first line treatment for OI, osteoporosis and metastatic bone disease, the duration and dosing of bisphosphonates varies for each condition. For example, zolendronic acid 4mg i.v. monthly is recommended for cancer patients with metastatic bone disease, while a dose of 5mg i.v. yearly is used for osteoporosis, depending on the severity. Additionally, no clear consensus exists for how often or how long bisphosphonates may be given in adults with OI and treatment durations vary markedly. Other agents that may be considered include denosumab, with indications across bone metastases, osteoporosis, and OI, though this was not available to our patient given her prior complication. Data for newer agents PTH analogs and romosuzumab are lacking. We present this case to highlight the need for an individualized treatment approach in these patients. Presentation: Thursday, June 15, 2023

SAT223 Persistent Hypocalcemia After Thyroidectomy

Abstract Disclosure: R. Subramani: None. F. Manas: None. A. Kauser: None. S. Yavuz: None. Introduction: Hypocalcemia is one of the serious complications after total thyroidectomy with a reported incidence of 27.4% (transient)and 12.1% (permanent) probably related to iatrogenic parathyroidectomy. Here we report a case of hypocalcemia after thyroidectomy in the setting of normal parathyroid hormone levels. Summary: A 42-year-old female with medical history of multinodular goiter s/p thyroidectomy 2019 on thyroid hormone replacement presented with hypocalcemia since 2021. During the first-year post thyroidectomy, patient was doing well until she acquired COVID-19 in 2020 and started developing symptoms of paresthesia, and muscle spasms. Other parameters such as phosphorus, and 25 OH vitamin D were normal. Despite being on a high-dose calcium supplement 1200 mg every hour for 10 times daily and calcitriol 0.75 mg twice daily, her calcium levels were persistently low ranging between 7.1 to 8 mg/dl and normal albumin levels of 3.9 and 4.3, but parathyroid level (PTH) remained normal (27.7-37.5). The patient was also symptomatic. She was later switched to liquid calcium 1000 mg 6 times daily for better absorption. It is noted that she had recurrent symptomatic hypocalcemia episodes requiring multiple emergency room (ER) visits during times of stress such as viral illness. The patient was treated with a trial of teriparatide, after which her symptoms improved and there were no further ER visits. Her calcium level increased from 7.4 to 8.4 and calcium supplement requirement reduced to 1200 mg daily. During recent outpatient visit, the patient had hypocalcemia episodes after missing teriparatide doses as expected. Conclusion: Despite our patient had normal PTH levels, the parathyroids glands did not respond appropriately to hypocalcemia. Promberger et al studied a case of eight patients with hypocalcemia with normal PTH following thyroidectomy. All these patients had normal PTH levels during post-op period, but persistently low and ionized calcium levels 12 months after surgery. This suggests during persistent hypocalcemia normal parathyroid levels may indicate an inadequate PTH response. In our case, developing hypocalcemia long after surgery and relation to COVID-19 infection may suggest autoimmune phenomenon as developing PTH-antibodies or receptor malfunction, theory yet to be investigated. In cases of severe symptomatic hypocalcemia requiring significant amount of calcium supplement PTH analogs are very effective treatment. Presentation: Saturday, June 17, 2023

Bariatric surgery and secondary hyperparathyroidism; a mini-review

Bariatric surgery is a type of weight loss surgery that is commonly used to treat obesity. However, this surgery can also affect the body’s calcium and PTH metabolism, leading to the development of secondary hyperparathyroidism (SHPT). Several factors contribute to the development of SHPT after bariatric surgery. Malabsorption of calcium due to reduced intestinal surface area, decreased intake of calcium-rich foods, and altered vitamin D metabolism play a significant role. The loss of weight-bearing adipose tissue can also disrupt the balance between bone formation and resorption, leading to increased bone turnover and calcium release from the skeleton. The management of SHPT after bariatric surgery involves a multidisciplinary approach. Calcium and vitamin D supplementation is essential to correct deficiency and maintain bone health. However, achieving optimal calcium and vitamin D levels can be challenging due to malabsorption issues and the need for higher supplementation doses. In some cases, pharmacological interventions such as calcimimetics or PTH analogs may be required to control PTH levels. However, these medications should be used cautiously due to limited data on their safety and efficacy in the bariatric surgery population. Prevention of SHPT is an important aspect of managing patients undergoing bariatric surgery. Nutritional counseling and regular monitoring of calcium, vitamin D, and PTH levels can help identify and address deficiencies early on. Additionally, using procedures that preserve the duodenum and proximal jejunum, such as duodenal switch or biliopancreatic diversion with duodenal switch, may reduce the risk of developing SHPT.

#5454 DESIGN AND OPTIMIZATION OF DRUG COMBINATION THERAPIES FOR OSTEOPOROSIS VIA SIMULATIONS OF BONE TURNOVER

Abstract Background and Aims Many chronic kidney disease (CKD) patients suffer from mineral and bone disorders like osteoporosis, which also affects a huge part of the general population, predominantly postmenopausal women. For the treatment of osteoporosis, several drug types with different mechanisms of action are available, such as bisphosphonates, PTH analogs, RANKL inhibitors and sclerostin inhibitors (some of which are contraindicated for CKD patients beyond CKD stage 3). Different drugs can be given individually or combined in various ways, simultaneously or sequentially, resulting in a huge number of theoretically possible drug combinations that are practically impossible to study in clinical studies. We aimed to study using simulations whether there are combination therapies that would work considerably better than those tested and employed in clinical practice. If so, this could be beneficial for the treatment of a large number of osteoporosis patients by leading to a higher increase in bone strength and a higher reduction in bone fracture risk than standard therapies. Method We developed a physiology-based mathematical model that simulates the process of bone renewal in the human body and can predict how different osteoporosis drugs (including bisphosphonates, PTH analogs, RANKL inhibitors, and sclerostin inhibitors) affect this process, alone and in combination [1]. Results The model was validated on over 30 clinical osteoporosis studies with about 90 study arms. It predicted the time courses of bone mineral density and bone turnover markers with a high degree of accuracy based on the knowledge of the used drugs and dosing schemes alone. We used the model to study how treatment results changed when merely reshuffling the order in which different drugs were given. For example, for 3-year drug therapies involving alendronate, denosumab and romosozumab (1 year each), our simulations showed that the order in which these drugs were given can have a considerable effect on short- and long-term therapy success [1]. This is due to different drugs favorably interacting when applied in the right sequence. Conclusion Our findings indicate that some osteoporosis drug administration schemes are superior to others while relying on the exact same types and amounts of drugs. Therefore, there is a large potential to improve pharmacologic therapies of osteoporosis using physiological simulations. For renal patients beyond CKD stage 3, a restricted set of drug types may be considered to account for contraindications related to impaired renal clearance. If translated into clinical practice, findings obtained using our model could give rise to novel treatments using combinations of existing drugs for osteoporosis that lead to a lower bone fracture risk than standard treatments. Moreover, our model could serve as a basis for personalizing osteoporosis therapy to individual patients.

Treatment options in hypoparathyroidism.

Hypoparathyroidism remains the single endocrine deficiency disease that is not habitually treated with the missing hormone. In this article, we aim to provide a review of the conventional approach and the novel therapies as well as an overview of the perspectives on the treatment of this rare condition. We conducted a literature review on the conventional therapy using vitamin D analogs and calcium salts, indications for thiazide diuretics and phosphorus binders, PTH analogs history and usage, and the drugs that are currently being tested in clinical trials. Conventional treatment involves calcium salts and vitamin D analogs. Thiazide diuretics can be used to reduce hypercalciuria in some cases. A low-phosphate diet is recommended, and phosphate binders are rarely needed. During pregnancy, a careful approach is necessary. The use of PTH analogs is a new approach despite the limitation of high cost. Studies have included modified PTH molecules, calcilytics, microencapsulation of human parathyroid cells, and allotransplantation.

Anabolic effects of rhPTH and novel PTH analog on titanium osseointegration and bone regeneration in ovariectomized beagle model

Anabolic effects of rhPTH and novel PTH analog on titanium osseointegration and bone regeneration in ovariectomized beagle model

Safety, tolerability and pharmacodynamics of AZP-3601, a novel long-acting PTH analog, in healthy adults: Data from a randomized, double-blind, placebo-controlled phase 1 study

Safety, tolerability and pharmacodynamics of AZP-3601, a novel long-acting PTH analog, in healthy adults: Data from a randomized, double-blind, placebo-controlled phase 1 study

Radiotherapy-Associated Pelvic Insufficiency Fracture Treated by Romosozumab: Course of L1 and L5 Vertebral Body CT Attenuation

Background: Radiotherapy is a risk factor for osteoporosis and insufficiency fractures via osteoblast apoptosis and vascular injury. PTH analogs teriparatide and abaloparatide are contraindicated in patients with prior exposure to radiotherapy crossing bone due to the increased risk of osteosarcoma. Patients with radiotherapy-associated fractures or osteoporosis were eligible only for antiresorptive agents until romosozumab was recently FDA-approved. Current International Society for Clinical Densitometry (ISCD) guidelines include assessment of “opportunistic CT” as a surrogate for DXA scan using L1 vertebral body attenuation: >150 Hounsfield units (HU) is normal and <100 HU signifies osteoporosis.Clinical Case: A 60 year old female patient with history of endometrial cancer diagnosed at age of 57 and treated with hysterectomy and bilateral salpingo-oophorectomy, chemotherapy, then pelvic radiotherapy, was referred to endocrinology for pelvic insufficiency fractures evaluation. Two years after completing chemoradiotherapy, she complained of right groin and low back pain with difficulty walking. MRI pelvis showed bilateral sacral ala and right pubic ramus insufficiency fractures. She had normal serum mineral concentration, 25-OH vitamin D sufficiency, normal PTH, eGFR, liver function tests and 24-hour urine calcium excretion. Screening for celiac disease and multiple myeloma was negative. DXA scan BMD T-score showed osteoporosis, -3.0 at the right femoral neck. L1-L4 T-score was +0.4 but unreliable due to presence of degenerative changes. Four months after onset of pain, patient started romosozumab 210mg SQ monthly for a total of 12 doses, after which she started oral alendronate. Pain essentially resolved within 6 months of romosozumab therapy. C-telopeptide (CTX) and procollagen type 1 N-terminal propeptide (P1NP) were obtained at baseline, 3 and 12 months after romosozumab initiation. CTX was 362, 247 and 258 pg/mL (reference range, >49 years: not established), and P1NP was 82, 178 and 62 mcg/L (reference range, 20 - 108), respectively. Attenuation of L1 and L5 vertebral body was measured using CT abdomen and pelvis scans before and 5 months after radiotherapy, and before and after completion of romosozumab therapy. L1 attenuation measured 161, 132, 127 and 179 HU, and L5 measured 150, 46, 50 and 86 HU, respectively.Conclusion: Pelvic radiotherapy was associated with a decline in L1 CT attenuation and even greater magnitude of decrease at L5. Romosozumab was associated with clinical improvement, restoration of L1 CT attenuation and diminishment of regain at L5. Although L5 attenuation has not been previously assessed for osteoporosis, this site may be of predictive value in patients who receive pelvic radiotherapy.

The challenges of post-bariatric surgery hypocalcaemia in pre-existing hypoparathyroidism.

SummaryConventional treatment of hypoparathyroidism relies on oral calcium and calcitriol. Challenges in managing post-parathyroid- and post-thyroidectomy hypocalcaemia in patients with a history of bariatric surgery and malabsorption have been described, but postoperative management of bariatric surgery in patients with established hypoparathyroidism has not. We report the case of a 46-year-old woman who underwent elective sleeve gastrectomy on a background of post-surgical hypoparathyroidism and hypothyroidism. Multiple gastric perforations necessitated an emergency Roux-en-Y gastric bypass. She was transferred to a tertiary ICU and remained nil orally for 4 days, whereupon her ionised calcium level was 0.78 mmol/L (1.11–1.28 mmol/L). Continuous intravenous calcium infusion was required. She remained nil orally for 6 months due to abdominal sepsis and the need for multiple debridements. Intravenous calcium gluconate 4.4 mmol 8 hourly was continued and intravenous calcitriol twice weekly was added. Euthyroidism was achieved with intravenous levothyroxine. Maintaining normocalcaemia was fraught with difficulties in a patient with pre-existing surgical hypoparathyroidism, where oral replacement was impossible. The challenges in managing hypoparathyroidism in the setting of impaired enteral absorption are discussed with analysis of the cost and availability of parenteral treatments.Learning points:Management of hypoparathyroidism is complicated when gastrointestinal absorption is impaired.Careful consideration should be given before bariatric surgery in patients with pre-existing hypoparathyroidism, due to potential difficulty in managing hypocalcaemia, which is exacerbated when complications occur.While oral treatment of hypoparathyroidism is cheap and relatively simple, available parenteral options can carry significant cost and necessitate a more complicated dosing schedule.International guidelines for the management of hypoparathyroidism recommend the use of PTH analogues where large doses of calcium and calcitriol are required, including in gastrointestinal disorders with malabsorption.Approval of subcutaneous recombinant PTH for hypoparathyroidism in Australia will alter future management.

Abstract 693: Effects of a bone-anabolic agent on metastatic bone cancer growth

Abstract Introduction: Cancer cells colonized to bone pathologically alter the bone niche to support the cancers' growth and survival. Multiple myeloma (MM) and metastatic solid tumors, particularly breast cancer (BC), activate osteoclasts and suppress osteoblasts leading to many complications and an increased mortality risk. Current strategies primarily target osteoclasts. Known osteoclast activating factor PTHrP is expressed by MM cells and BC cells and may contribute to progression. We hypothesized that alteration of PTH receptor signaling should overcome cancers' inhibition of bone formation and decrease cancer growth in bone. BDDP, a novel PTH analog, is being developed for osteoporosis treatment. We determined the ability of BDDP to reverse osteoblast suppression and slow tumor growth in bone with MM and BC models. Methods: In vitro effects of BDDP on bone genes and bone mineralization were tested in a co-culture assay of osteoblastic MC3T3-E1 cells ± human MM.1s cells. After 3 days in proliferative media, they were cultured in differentiation media. At Day 7, the expression of genes with known roles in osteoblast differentiation were assayed by RT-PCR. At Day 25, nodular calcification was stained and measured by a colorimetric assay. In vivo effects of BDDP were evaluated in an intratibial transplant model. MDA-MB-231 BC cells expressing secreted luciferase were injected into the ipsilateral tibiae of Balb/cnu/nu mice. Mice received either BDDP (40μg/kg/d) or vehicle via osmotic pump for 30 days. After euthanasia, mice were subjected to Faxitron digital X-rays to detect osteolytic lesions and DEXA scans to assess bone mineral content (BMC) and bone mineral density (BMD). Tumor-injected and non-injected tibiae were subjected to micro-QCT for 3D tibiae imaging. Results: MM.1s-treated MC3T3-E1 cells showed approximately a 5-fold reduction in osteoblast differentiation gene RUNX2 and a 3-fold reduction in BGLAP. This effect was attenuated by 100 nM BDDP by approximately 4-fold in both Runx2 and BGLAP. BDDP increased nodular calcification. Nodular calcification was suppressed in MM.1s-treated MC3T3-E1 cells. This effect was reversed by BDDP. BDDP did not directly affect MM.1s and MDA-MB-231 growths in culture but showed dramatic tumor suppression in a MDA-MB-231 intratibial transplant model. Tumor burden assayed by serial serum luciferase assay showed BDDP-treated group to be 95% lower than control, at 3 and 4 weeks post-transplant. Tumor-injected tibiae had lytic lesions in all control mice, while there were no obvious lesions in BDDP-treated mice. There were no significant changes in the trabecular bone of non-injected tibiae, whole body composition, BMC or BMD. Conclusion: BDDP reverses osteoblastic suppression by MM cells in vitro, as well as inhibiting tumor growth and preventing local bone destruction in the BC intratibial transplant model, thereby making BDDP a promising potential treatment strategy for metastatic bone cancers. Citation Format: Teja Vallapuri, Colin Crean, John Chirgwin, G. David Roodman, Attaya Suvannasankha. Effects of a bone-anabolic agent on metastatic bone cancer growth [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 693.

Optimization of PTH/PTHrP Hybrid Peptides to Derive a Long-Acting PTH Analog (LA-PTH).

ABSTRACTProlonged signaling at the parathyroid hormone receptor 1 (PTHR1) correlates with the capacity of a ligand to bind to a G protein‐independent receptor conformation (R0). As long‐acting PTH (LA‐PTH) ligands hold interest as potential treatments for hypoparathyroidism (HP), we explored the structural basis in the ligand for stable R0 binding and prolonged cAMP signaling. A series of PTH/PTHrP hybrid analogs were synthesized and tested for actions in vitro and in vivo. Of the series, [Ala1,3,12,Gln10,Arg11,Trp14]‐PTH(1‐14)/PTHrP(15–36) (M‐PTH/PTHrP) bound with high affinity to R0, induced prolonged cAMP responses in UMR106 rat osteoblast‐derived cells, and induced the most prolonged increases in serum calcium (sCa) in normal rats. Daily s.c. injection of M‐PTH/PTHrP into thyroparathyroidectomized (TPTX) rats, a model of HP, normalized sCa without raising urine Ca. In contrast, oral alfacalcidol, a widely used treatment for HP, normalized sCa, but induced frank hypercalciuria. M‐PTH/PTHrP exhibited low solubility in aqueous solutions of neutral pH; however, replacement of Leu18, Phe22, and His26 with the less hydrophobic residues, Ala, Ala, and Lys, at those respective positions markedly improved solubility while maintaining bioactivity. Indeed, we recently showed that the resultant analog [Ala18,22,Lys26]‐M‐PTH/PTHrP or LA‐PTH, effectively normalizes sCa in TPTX rats and mediates prolonged actions in monkeys. These studies provide useful information for optimizing PTH and PTHrP ligand analogs for therapeutic development. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

SAT-396 A Non-Surgical Animal Model of Hypoparathyroidism for Testing PTH Analogues

BACKGROUND:In vivo animal models for testing the pharmacokinetics and bioactivity of PTH and its analogues require parathyroidectomy by surgery (1, 2). As the parathyroid glands of rodents are very small the surgery often includes thyroidectomy, making this animal model time-limited, single use, complex, and expensive. We have developed a non-surgical rodent model of hypoparathyroidism using the Type II calcimimetic compound, Cinacalcet-HCl, to suppress PTH and thereby serum calcium levels.Methods:Normal male Wistar rats were gavaged with 30 mg/kg Cinacalcet-HCl (or vehicle only). To test the effect of PTH 1–34, animals were dosed immediately after Cinacalcet-HCl gavage with either a single subcutaneous injection of PTH at 20 nmol/kg or given as same dose repeated every hour for 6 hrs or vehicle only. Serum samples were analysed for ionised calcium (iCa) using an EasyLyte, fully automated electrolyte analyser (Medica Corporation) and phosphate using a Phosphorus Detection Assay Kit (Pars Azmun, IRAN) and an Hitachi 917 Clinical Chemistry Analyser.Results:Rats gavaged with 30 mg/kg Cinacalcet-HCl produced a significant reduction in iCa levels between 2-24hrs returning to baseline at 48-72hrs post dose with the nadir at 8 hours (ANOVA P < 0.0001). This equated to a 25% reduction in iCa at 8 hrs: mean±SD, iCa 1.19 ± 0.09 mmol/L at predose and 0.891 ± 0.04 mmol/L at 8 hours (t-test P < 0.0001). For phosphate there was an initial lowering within the first 2 hrs in all test groups but then a rise such that phosphate was at higher levels than control from 8–24 hrs (ANOVA, ns), returning to baseline at 48 hrs. PTH at 20 nmol/kg given as a single sc dose abrogated the Cinacalcet-HCl induced fall in iCa for up to 2 hrs (AUC±SD (mmol/L).hr, 0.076 ±0.047 versus 0.168±0.0874, t-test P=0.0289).Conclusions:We have shown that the administration of Cinacalcet-HCl provides a robust and reproducible lowering of calcium which is line with current published data (3). These studies demonstrate that the use of Cinacalcet-HCl in normal rats produces a hypocalcemic state that can be abrogated by the addition of PTH. This non-surgical animal model of hypoparathyroidism will be of value in testing the pharmacodynamics of PTH analogues.

MON-358 Hypercalcemia During Teriparatide Therapy

Background: Teriparatide (TPTD) is a recombinant PTH analog used as an anabolic agent in the treatment of osteoporosis that stimulates bone formation and activates bone remodeling. The most common side effects are nausea, vomiting, hypertension and dizziness. Transient hypercalcemia is a known adverse effect which is usually seen a few hours after administration and resolves within 16 hours. However, marked late hypercalcemia is a rare event and may be of concern in clinical practice. Clinical Cases: Case 1 is a 54-year-old man with a history of osteoporosis (lumbar spine T-score of -2.8), previously treated with bisphosphonates and who had been on a course of TPTD for about 6 months in but had not been consistent in taking the medication. Prior to subsequently restarting TPTD, his initial labs were notable for a normal Ca 9.3 mg/dl (8.5 - 10.1 mg/dl), vitamin D 25 OH 49 ng/ml (30.0 - 100.0 ng/ml) and PTH 41.3 pg/ml (8.7 - 77.1 pg/ml). Six months into the treatment, he was noted to have asymptomatic hypercalcemia of 11.2 mg/dl approximately 24 hrs after the last TPTD injection. A repeat calcium of 10.7 mg/dl was obtained while still on therapy with TPTD with normal levels of vitamin D 25 OH of 45 ng/ml. Case 2 is a 75-year-old woman with a history of osteopenia and severe scoliosis, who had been on a course of raloxifene and then preventive doses of alendronate previously. Prior to starting TPTD, her Ca levels were normal at 9.3 mg/dl, PTH was 24 pg/ml and vitamin D 25 OH was 33 ng/ml. However, six months into the treatment she was noted to have elevated Ca of 12.5 mg/dl (24 hrs after the last TPTD dose), with low levels of vitamin D 25 OH of 24.2 ng/ml. Ca levels returned to the baseline of 9.3 mg/dl when TPTD was held. Conclusion: Teriparatide has a long track record of safety and does have the rare side effect of hypercalcemia. 1-3% of patients may have mild hypercalcemia after administration. Intake of calcium and vitamin D should be monitored at the start of therapy given these concerns. Although almost never a cause of discontinuation of treatment in clinical practice, it is important to be aware of this side effect in patients who may be at risk of complications of hypercalcemia.

HPTH(3-34)(29-34) selectively activated PKC and mimicked osteoanabolic effects of hPTH(1-34).

Teriparatide (hPTH(1-34)) exhibits both osteoanabolic and osteocatabolic effects. We generated a novel PTH analog by duplicating the PTH(29-34) domain to hPTH(3-34) (named MY-1), which was identified to activate PKC but not PLC and cAMP/PKA signaling. It increased osteo-differentiation but did not affect osteoclastogenesis and RANKL expression in primary osteoblasts or bone marrow cells. MY-1 and hPTH(1-34) increased the synthesis and decreased the degradation οf β-catenin protein in osteoblasts, while PKC inhibitor blunted such effects. In vivo results indicated that intermittent MY-1 and hPTH(1-34) prevented bone loss in ovariectomized mice, and that MY-1 infusion increased bone volume in normal mice. Histological analysis observed more osteoclasts surrounding the cancellous bone surface in hPTH(1-34), but not MY-1 treated mice. We conclude that MY-1 mimicked the osteoanabolic but not the osteocatabolic effects of hPTH(1-34), which is related to PKC and β-catenin signaling. Such anabolic-only analog provides a new strategy to study PTH's versatile functions and design new medicines to treat osteoporosis and bone defects.