Company: WHWK
Filing Date: 2025-01-21
Form Type: PREM14A
Source: 0001193125-25-009599
Chunk: 291

Company: Whitehawk Therapeutics, Inc.
Filing Date: 2025-01-21
Form: PREM14A
Chunk 291
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”), progression free survival (“PFS”) and overall survival (“OS”). The sample size estimation assumed an observed ORR of 30% for a sample size of 30
patients, which would exclude values less than 14.7% for the lower bound of the 95% confidence interval.

This registrational trial met its primary
endpoint demonstrating the efficacy of nab-sirolimus in this rare disease for which there was no FDA approved treatment, with an independently assessed ORR of 39% (95% CI: 22%, 58%). Disease control (defined as complete or partial response
(“CR” or “PR”) + stable disease ≥12 weeks) was achieved in 71% of patients. FYARRO (nab-sirolimus) was subsequently approved by the FDA for the treatment of advanced malignant PEComa on November 22, 2021.

Sixty-seven percent (8 of 12) of responses were seen at the first scan after baseline at week six (median time to response 1.4 months, 95% CI: 1.3 to 2.8
months). At the time of the primary analysis (predefined as when all patients had an opportunity to be treated for 6 months), the median for the key secondary endpoint of DOR was

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not yet reached, with 9 of 12 responders still on treatment (DOR range 4.2+, 27.7+ months). At 1.5-years of
follow-up after the primary analysis date (i.e., 2-years after the last patient-initiated treatment), 7 of 12 responders were still receiving treatment and the median
DOR was still not reached, with 50% of patients exceeding 2.5 years (DOR range 5.6, 47.2+ months).

Figure 9 shows the target tumor responses (waterfall
plot). One patient with a primary renal PEComa metastatic to the lungs and lymph nodes had a PR for 10 months that converted to a CR. Responses were independent of the primary site and were observed in tumors originating in the uterus (3), kidney
(3), retroperitoneum (2), pelvis (2), liver (1), and small bowel (1). Notably, 43% (3/7) of patients with uterine PEComa had a partial response. Responses were also observed in 3/4 patients who had previously received chemotherapy