Endocrine Abstracts

JOINT2461

Introduction: Parathyroid hormone (PTH) replacement therapy is a relatively new treatment option for chronic hypoparathyroidism (HypoPT). As the previously approved rhPTH1-84 is no longer manufactured, patients need to switch to an alternative replacement therapy. Palopegteriparatide (TransCon PTH) is a long-acting, slow-release molecule of PTH1-34 that was recently approved by the EMA and FDA. In this retrospective multicenter study, we describe our experience with the initial phase of switching from rhPTH1-84 to TransCon PTH.

Methods: We analyzed data from 40 patients with chronic postsurgical HypoPT (n = 37) or nonsurgical (n = 3) HypoPT during the change of treatment. In Germany, rhPTH1-84 treatment was only available for patients not adequately controlled through conventional therapy or with complications, and only few patients received the expensive treatment. TransCon PTH was available during a compassionate-use program or used after officially becoming available in Germany starting January 2024. Independently of the last prior rhPTH-1-84 dose, all patients were started on 18 µg of TransCon PTH with dose adaptation, and adverse events were documented.

Results: Within the first month of transition, 80% (n = 32) of patients needed individual adjustment of their TransCon PTH dose. Specifically, 38% needed a dose reduction to between 9 and 15 µg, while 43% (n = 17) required an increase to 21-27 µg. Adjustments by treating physicians was based on serum calcium levels with the goal of calcium in the lower normal range (in 62 % cases), or dependent on symptoms. The previous rhPTH1-84 dose correlated positively with the adjusted TransCon PTH dose (r = 0.4; P = 0.01). The treatment change was associated with moderate or mild symptoms. From 34 patients documented, 38% (n = 13) reported headache, 38% (n = 13) muscular spasms or arthralgia, 24% sleep disturbance or fatigue, 21% (n = 7) nausea, 21% palpitations, 15% injections site reactions, and 15% other gastrointestinal symptoms (n = 5). Ten patients reported no negative symptoms.

Conclusion: Switching treatment from rhPTH1-84 to TransCon PTH using the initial dose of 18 µg proved to be efficient independently of the prior rhPTH1-84 dose. Adverse events were frequent, albeit mild to moderate and no patient withdrew from treatment.