Trastuzumab Model Measures Expanded Access With Ogivri Biosimilar

June 24, 2021

Article

Investigators determine that converting at least 2 patients with metastatic breast cancer to a trastuzumab biosimilar could generate savings enough to treat a third patient.

A cost-efficiency analysis of a hypothetical cohort of 1000 US patients found that converting 2 patients with metastatic breast cancer (MBC) from reference trastuzumab (Herceptin) therapy to a trastuzumab biosimilar (Ogivri) could save enough money to pay for a full year of trastuzumab biosimilar monotherapy for an additional patient.

In the setting of trastuzumab in combination with pertuzumab (Perjeta) and paclitaxel, fewer than 3 patients would need to be converted to trastuzumab biosimilar to generate savings sufficient for a full year of combination therapy (Table).

Arguably, biosimilars approved in well-regulated markets, and therefore regulatorily assured to be equivalently effective and safe, should be recognized internationally as cost-responsible and affordable ways of expanding access to supportive and therapeutic cancer care in economically constrained countries.

The investigators analyzed cost-efficiency and budget-neutral expanded access from conversion of either intravenous (IV) or subcutaneous (SC) Herceptin to biosimilar trastuzumab.

“The marked cost savings achieved by biosimilar conversion to [Ogivri] can be re-allocated to provide expanded access to additional doses or year-long regimens of trastuzumab-dkst on a budget-neutral basis,” the authors wrote.

Trastuzumab is a monoclonal antibody targeting human epidermal growth factor receptor 2 (HER2) that is approved for the treatment of HER2-positive early and advanced MBC. In MBC, trastuzumab is used as monotherapy in patients who have received 1 or more chemotherapy regimens. It is also used in combination with pertuzumab and taxane-based chemotherapy.

Writing in Journal of Medical Economics, the authors said that although the availability of biologics has “significantly advanced cancer treatment options and outcomes,” the high cost of originator trastuzumab contributes to “significant disparities in access to anti-HER2 therapy in resource-limited communities.”

The investigators calculated savings based on 10% to 100% conversion rates from Herceptin IV and SC formulations to Ogivri in patients stratified by body weight quartiles: 25th percentile, median weight 137 lb; 50th percentile, 161 lb; and 75th percentile, 195 lb. Those weight groupings were labeled Q1, Q2, and Q3, respectively, for purposes of the study.

Trastuzumab Monotherapy

On a cost-of-drug basis only, conversion from IV Herceptin to the biosimilar produced 1-year savings ranging from $2,272,189 at 10% conversion among Q1 patients to $31,506,804 at 100% conversion rate for Q3 patients. Including both drug and administration costs, the savings were identical: $2,272,189 to $31,506,804.

Conversion from the SC formulation produced an estimated range of 1-year drug cost savings of $2,071,277 at 10% conversion in Q3 patients to $35,775,475 at 100% conversion in Q1 patients. Including both drug and administration costs, savings ranged from $564,347 to $20,706,175.

Trastuzumab With Pertuzumab and Paclitaxel

Estimated 1-year drug cost savings for conversion from trastuzumab-IV to Ogivri for combination therapy with pertuzumab (all cycles) and paclitaxel (cycles 1-4) in the hypothetical patient cohort ranged from $2,298,610 with 10% conversion in Q1 patients to $32,662,714 at a 100% conversion rate in Q3 patients. Incorporating administration costs, the corresponding range of savings was $2,298,610 to $32,662,714.

For conversion from trastuzumab-SC to Ogivri used in combination with pertuzumab and paclitaxel, 1-year drug cost savings ranged from $1,873,083 with 10% conversion in Q3 patients to $35,322,461 with 100% conversion in Q1 patients. For drug-plus-administration costs, savings were $1,764,255 to $34,234,181.

Number Needed to Convert

The investigators went on to calculate the number of patients needed to be converted (NNC) to the biosimilar to generate savings enough to purchase equivalent therapy for 1 additional patient.

Considering drug costs only, the NNC from trastuzumab-IV was 1.71 to purchase a full year of trastuzumab biosimilar monotherapy in all weight categories. The NNC from trastuzumab-SC was 1.09 in Q1 patients, 1.51 in Q2 patients, and 2.61 in Q3 patients.

Including both drug and administration costs of trastuzumab monotherapy, the NNC was 2.23 in Q3 patients, 2.33 in Q2 patients, and 2.43 in Q1 patients for conversion from trastuzumab-IV. For conversion from trastuzumab-SC, the NNC was 2.66 in Q1 patients, 4.18 in Q2 patients, and 12.44 in Q3 patients.

For 1 year of combination therapy (trastuzumab biosimilar, pertuzumab, and paclitaxel), the drug-cost-only NNC from trastuzumab-IV was 4.77 in Q3 patients, 5.46 in Q2 patients, and 6.05 in Q1 patients.

The NNC from trastuzumab-SC to provide 1 full year of combination therapy was 3.94 in Q1 patients, 5.01 in Q2 patients, and 8.32 in Q3 patients. Including both drug and administration costs, the NNC from trastuzumab-IV were 5.03, 5.77, and 6.42, while they were 4.31, 5.51, and 9.31 for conversion from trastuzumab-SC.

Budget-Neutral Expanded Access

At a 100% rate of conversion from trastuzumab-IV to the biosimilar, the simulation model estimated a full, 1-year regimen of biosimilar monotherapy could be provided to 583 additional patients (any weight group) considering drug costs only.

Including administration costs, the estimate was that 412 to 449 additional patients could receive therapy, depending on body weight category.

For conversion from trastuzumab-SC, estimates for expanded access based on drug costs only ranged from 383 to 918 additional patients, based on body weight. Including both drug and administration costs, 80 to 376 additional patients could receive a full year of monotherapy on a budget-neutral basis.

This economic simulation demonstrates that biosimilar trastuzumab is cost-efficient over trastuzumab-IV and trastuzumab-SC across all patient weights in both monotherapy and in combination with pertuzumab and paclitaxel.

For combination therapy, up to 210 (drug costs only) or 199 (drug and administration costs) full-year regimens of combination therapy could be purchased based on a 100% rate of conversion from trastuzumab-IV to biosimilar trastuzumab. For conversion from trastuzumab-SC, up to 254 and 232 patients, respectively, could be provided with a full year of combination therapy.

The investigators viewed their contribution as significant as the “first cost-efficiency and expanded access study” of these biologic drugs. They contended the cost savings and “low” NNC figures estimated by their model could translate into substantial expanded access to biosimilar trastuzumab therapy.

They emphasized that based on their drug-costs-only model, fewer than 2 patients need to be converted from trastuzumab-IV to provide an additional patient with a full year of trastuzumab monotherapy with the biosimilar agent.

Reference

McBride A, MacDonald K, Fuentes-Alburo A, Abraham I. Cost-efficiency and expanded access modeling of conversion to biosimilar trastuzumab-dkst with or without pertuzumab in metastatic breast cancer. J Med Econ. 2021;24(1):743-756. doi:10.1080/13696998.2021.1928515