Five-year follow-up of OPTIC: long-term efficacy, safety, and mutation analyses of ponatinib in chronic-phase chronic myeloid leukemia from a randomized phase 2 trial

From Potent Therapy to Optimized Strategy: The OPTIC Story

The introduction of BCR::ABL1 tyrosine kinase inhibitors (TKIs) transformed chronic myeloid leukemia (CML) from a fatal disease into a chronic condition.^1-3 However, important challenges remained for patients who developed resistance after multiple lines of therapy or who harbored the T315I mutation, which confers resistance to all TKIs approved prior to the development of ponatinib.^4,5

Ponatinib was designed to inhibit BCR::ABL1, including the T315I gatekeeper mutation,⁶ and has demonstrated efficacy in heavily pretreated patients with chronic-phase (CP)-CML.⁷ While the development of ponatinib represents a major advance, the story of ponatinib over the past decade has focused on optimizing its use by minimizing toxicity while maintaining efficacy. Our recently published five-year follow-up from the OPTIC trial marks the latest chapter in that story about balancing efficacy, safety, and long-term disease control, which may provide lessons that can be extended to the use of other TKIs in CML.

Promise From PACE

When the phase 2 PACE trial was initiated, patients with resistant CML had limited treatment options. PACE demonstrated that ponatinib 45 mg daily could overcome some of the most difficult treatment challenges in CML.

Responses were observed regardless of baseline mutation status, including in patients with T315I mutations. Importantly, no single BCR::ABL1 mutation conferring resistance to ponatinib was identified. By 12 months, 56% of patients had achieved a major cytogenetic response.⁷

While long-term follow-up confirmed durable efficacy,⁸ establishing ponatinib as a TKI available for resistant disease, the challenge became preserving that efficacy while improving long-term treatment management.

The Challenge

As clinical experience accumulated, arterial occlusive events (AOEs) emerged as an important consideration, with the cumulative incidence of AOEs being 31% at the five-year follow-up of PACE.⁸ Until that point, AOEs had not been recognized as an adverse event with TKIs, marking a new chapter of awareness and the need to address comorbidities in patients with CML. While many events occurred in patients with pre-existing cardiovascular risk factors, clinicians nonetheless faced a dilemma familiar throughout oncology: how could the benefits of a highly active therapy be maintained while minimizing risk?

Longer-term follow-up from PACE began to provide clues. Although most patients required dose reductions or interruptions during treatment, efficacy was often maintained.⁸ Analyses suggested that AOE risk was related to dose intensity,⁹ and raised the possibility that efficacy and safety might be improved through response-based dosing.

A Different Approach to Ponatinib Dosing

These observations provided the rationale for OPTIC, which tested a response-based dosing strategy. Patients with CP-CML who had received at least two prior TKIs or harbored a T315I mutation were randomized to starting doses of 45 mg, 30 mg, or 15 mg daily. Upon achieving ≤1% BCR::ABL1^IS, patients in the 45-mg and 30-mg cohorts underwent mandatory dose reduction to 15 mg.¹⁰

The goal was straightforward: maximize disease control early, then reduce long-term exposure to minimize toxicity while maintaining response.

Notably, this was a challenging patient population. More than half of patients (55%) had received three or more prior lines of TKI therapy, reflecting the refractory nature of the disease and the unmet need despite multiple available TKIs. Additionally, approximately one-third of patients had cardiovascular risk factors.¹⁰

Initial OPTIC results suggested that the 45-mg-to-15-mg strategy provided the optimal balance between efficacy and safety. At 12 months, 44.1% of patients in the 45-mg cohort achieved the primary endpoint of ≤1% BCR::ABL1^IS, the highest rate among the three dosing groups. Additionally, 9.6% of patients in the 45-mg cohort experienced an AOE.¹⁰

However, an important question remained: would these efficacy and tolerability benefits persist in the long term?

Five Years Later: Validation of the Strategy

The five-year OPTIC analysis provides strong evidence. Patients treated with the 45-mg-to-15-mg response-based regimen achieved the highest rates of molecular response. By five years, 60% of patients in the 45-mg cohort had achieved ≤1% BCR::ABL1^IS, compared with 41% and 40% in the 30-mg and 15-mg cohorts, respectively, demonstrating that responses achieved early in treatment could be maintained after dose reduction. Even among the difficult-to-treat subgroup of patients with baseline T315I mutations, cumulative response rates reached 64% in the 45-mg cohort. Another important finding is related to survival. Across the three dosing regimens, survival at five years exceeded 80%, and while survival rates were higher in the 45-mg cohort in patients with T315I mutations, they were similar across dosing regimens in patients with no mutations or non-T315I mutations.

The central findings observed at one year remained largely unchanged at five years. The efficacy advantages seen with the 45-mg-to-15-mg strategy persisted, while the safety profile remained manageable over long-term follow-up. Importantly, in OPTIC, the exposure-adjusted incidence rate of AOEs per 100 patient years with the 45-mg starting dose was nearly equivalent to that with the 30-mg starting dose (4.1 and 3.8, respectively), which is approximately half the value in PACE (8.9). Long-term exposure in OPTIC did not reveal new safety concerns, evidence of cumulative toxicity, or a meaningful increase in exposure-adjusted rates of AOEs, supporting the premise that efficacy could be preserved while reducing long-term treatment risk.

These results suggest that clinicians can maintain confidence in the response-based dosing strategy, knowing that the benefit–risk profile observed early in treatment remains largely intact over time.

The Mutation Story

One of the most interesting findings from OPTIC involves mutation analyses.

Ponatinib remains unique among currently available TKIs in that no specific single point mutation has been consistently identified that precludes its activity. In OPTIC, responses were observed regardless of baseline mutation status, including in patients with T315I mutations.

The end-of-treatment mutation analyses provided insight into long-term disease control. The majority of patients who discontinued treatment due to lack of efficacy or progressive disease (72/83) did not develop new mutations during therapy, and those without detectable mutations at baseline generally remained mutation-free (31/36). Mutations no longer detectable at the end of treatment were consistent with prior cellular studies demonstrating ponatinib’s activity against multiple mutation types.⁶ Interestingly, a few combined mutations (T315I in combination with another mutation) emerged, suggesting ponatinib may be best used as early as indicated before mutations develop.

Although limitations such as small sample sizes need to be considered when interpreting these data, the findings suggest that effective suppression of BCR::ABL1 may also suppress the emergence of new mutations and may result in the elimination of some existing mutations. They also support the importance of achieving effective disease control before increasingly complex mutational patterns develop.

Looking Forward

The question from PACE was whether clinicians could preserve the efficacy of ponatinib while improving long-term toxicity and treatment management. Five years later, OPTIC provides evidence that this may be achievable.

But the significance of OPTIC extends beyond this one study’s specific dosing regimen. At its core, OPTIC demonstrates that treatment optimization can be achieved without sacrificing efficacy, and that potent early disease control and long-term treatment management do not need to be competing objectives.

OPTIC represents one of the first prospective demonstrations of response-based dosing in CML. Rather than maintaining treatment intensity indefinitely, therapy can be adapted according to disease response while preserving clinical benefit. This reflects the broader concept of optimal biologic dosing: identifying the dose required to achieve and maintain meaningful disease control, rather than simply administering the highest tolerated dose over time. This principle may have implications not only for ponatinib, but for future targeted therapies.

PACE established ponatinib as a treatment option for resistant CML. OPTIC showed how to refine its clinical use. Together, these studies illustrate the evolution of ponatinib from a therapy with significant benefit and risk into a more precisely optimized treatment strategy, particularly for patients with resistant disease and those harboring T315I mutations.

References

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